diff --git a/crates/nu-command/src/core_commands/register.rs b/crates/nu-command/src/core_commands/register.rs
index e0750735c1..d175480b56 100644
--- a/crates/nu-command/src/core_commands/register.rs
+++ b/crates/nu-command/src/core_commands/register.rs
@@ -21,12 +21,6 @@ impl Command for Register {
                 SyntaxShape::Filepath,
                 "path of executable for plugin",
             )
-            .required_named(
-                "encoding",
-                SyntaxShape::String,
-                "Encoding used to communicate with plugin. Options: [json, msgpack]",
-                Some('e'),
-            )
             .optional(
                 "signature",
                 SyntaxShape::Any,
@@ -64,12 +58,12 @@ impl Command for Register {
         vec![
             Example {
                 description: "Register `nu_plugin_query` plugin from ~/.cargo/bin/ dir",
-                example: r#"register -e json ~/.cargo/bin/nu_plugin_query"#,
+                example: r#"register ~/.cargo/bin/nu_plugin_query"#,
                 result: None,
             },
             Example {
                 description: "Register `nu_plugin_query` plugin from `nu -c`(plugin will be available in that nu session only)",
-                example: r#"let plugin = ((which nu).path.0 | path dirname | path join 'nu_plugin_query'); nu -c $'register -e json ($plugin); version'"#,
+                example: r#"let plugin = ((which nu).path.0 | path dirname | path join 'nu_plugin_query'); nu -c $'register ($plugin); version'"#,
                 result: None,
             },
         ]
diff --git a/crates/nu-parser/src/parse_keywords.rs b/crates/nu-parser/src/parse_keywords.rs
index 4768dacac1..8ec660988e 100644
--- a/crates/nu-parser/src/parse_keywords.rs
+++ b/crates/nu-parser/src/parse_keywords.rs
@@ -3027,7 +3027,7 @@ pub fn parse_register(
     spans: &[Span],
     expand_aliases_denylist: &[usize],
 ) -> (Pipeline, Option<ParseError>) {
-    use nu_plugin::{get_signature, EncodingType, PluginDeclaration};
+    use nu_plugin::{get_signature, PluginDeclaration};
     use nu_protocol::{engine::Stack, Signature};
 
     let cwd = working_set.get_cwd();
@@ -3120,22 +3120,7 @@ pub fn parse_register(
                 }
             }
         })
-        .expect("required positional has being checked")
-        .and_then(|path| {
-            call.get_flag_expr("encoding")
-                .map(|expr| {
-                    EncodingType::try_from_bytes(working_set.get_span_contents(expr.span))
-                        .ok_or_else(|| {
-                            ParseError::IncorrectValue(
-                                "wrong encoding".into(),
-                                expr.span,
-                                "Encodings available: json, and msgpack".into(),
-                            )
-                        })
-                })
-                .expect("required named has being checked")
-                .map(|encoding| (path, encoding))
-        });
+        .expect("required positional has being checked");
 
     // Signature is an optional value from the call and will be used to decide if
     // the plugin is called to get the signatures or to use the given signature
@@ -3196,7 +3181,7 @@ pub fn parse_register(
     let current_envs =
         nu_engine::env::env_to_strings(working_set.permanent_state, &stack).unwrap_or_default();
     let error = match signature {
-        Some(signature) => arguments.and_then(|(path, encoding)| {
+        Some(signature) => arguments.and_then(|path| {
             // restrict plugin file name starts with `nu_plugin_`
             let f_name = path
                 .file_name()
@@ -3204,7 +3189,7 @@ pub fn parse_register(
 
             if let Some(true) = f_name {
                 signature.map(|signature| {
-                    let plugin_decl = PluginDeclaration::new(path, signature, encoding, shell);
+                    let plugin_decl = PluginDeclaration::new(path, signature, shell);
                     working_set.add_decl(Box::new(plugin_decl));
                     working_set.mark_plugins_file_dirty();
                 })
@@ -3212,14 +3197,14 @@ pub fn parse_register(
                 Ok(())
             }
         }),
-        None => arguments.and_then(|(path, encoding)| {
+        None => arguments.and_then(|path| {
             // restrict plugin file name starts with `nu_plugin_`
             let f_name = path
                 .file_name()
                 .map(|s| s.to_string_lossy().starts_with("nu_plugin_"));
 
             if let Some(true) = f_name {
-                get_signature(path.as_path(), &encoding, &shell, &current_envs)
+                get_signature(path.as_path(), &shell, &current_envs)
                     .map_err(|err| {
                         ParseError::LabeledError(
                             "Error getting signatures".into(),
@@ -3231,12 +3216,8 @@ pub fn parse_register(
                         for signature in signatures {
                             // create plugin command declaration (need struct impl Command)
                             // store declaration in working set
-                            let plugin_decl = PluginDeclaration::new(
-                                path.clone(),
-                                signature,
-                                encoding.clone(),
-                                shell.clone(),
-                            );
+                            let plugin_decl =
+                                PluginDeclaration::new(path.clone(), signature, shell.clone());
 
                             working_set.add_decl(Box::new(plugin_decl));
                         }
diff --git a/crates/nu-plugin/src/plugin/declaration.rs b/crates/nu-plugin/src/plugin/declaration.rs
index c47b9003f2..9657f4959d 100644
--- a/crates/nu-plugin/src/plugin/declaration.rs
+++ b/crates/nu-plugin/src/plugin/declaration.rs
@@ -1,6 +1,6 @@
-use crate::{EncodingType, EvaluatedCall};
+use crate::EvaluatedCall;
 
-use super::{call_plugin, create_command};
+use super::{call_plugin, create_command, get_plugin_encoding};
 use crate::protocol::{
     CallInfo, CallInput, PluginCall, PluginCustomValue, PluginData, PluginResponse,
 };
@@ -16,21 +16,14 @@ pub struct PluginDeclaration {
     signature: Signature,
     filename: PathBuf,
     shell: Option<PathBuf>,
-    encoding: EncodingType,
 }
 
 impl PluginDeclaration {
-    pub fn new(
-        filename: PathBuf,
-        signature: Signature,
-        encoding: EncodingType,
-        shell: Option<PathBuf>,
-    ) -> Self {
+    pub fn new(filename: PathBuf, signature: Signature, shell: Option<PathBuf>) -> Self {
         Self {
             name: signature.name.clone(),
             signature,
             filename,
-            encoding,
             shell,
         }
     }
@@ -111,17 +104,27 @@ impl Command for PluginDeclaration {
             input,
         });
 
-        let response =
-            call_plugin(&mut child, plugin_call, &self.encoding, call.head).map_err(|err| {
-                let decl = engine_state.get_decl(call.decl_id);
-                ShellError::GenericError(
-                    format!("Unable to decode call for {}", decl.name()),
-                    err.to_string(),
-                    Some(call.head),
-                    None,
-                    Vec::new(),
-                )
-            });
+        let encoding = {
+            let stdout_reader = match &mut child.stdout {
+                Some(out) => out,
+                None => {
+                    return Err(ShellError::PluginFailedToLoad(
+                        "Plugin missing stdout reader".into(),
+                    ))
+                }
+            };
+            get_plugin_encoding(stdout_reader)?
+        };
+        let response = call_plugin(&mut child, plugin_call, &encoding, call.head).map_err(|err| {
+            let decl = engine_state.get_decl(call.decl_id);
+            ShellError::GenericError(
+                format!("Unable to decode call for {}", decl.name()),
+                err.to_string(),
+                Some(call.head),
+                None,
+                Vec::new(),
+            )
+        });
 
         let pipeline_data = match response {
             Ok(PluginResponse::Value(value)) => {
@@ -134,7 +137,6 @@ impl Command for PluginDeclaration {
                         data: plugin_data.data,
                         filename: self.filename.clone(),
                         shell: self.shell.clone(),
-                        encoding: self.encoding.clone(),
                         source: engine_state.get_decl(call.decl_id).name().to_owned(),
                     }),
                     span: plugin_data.span,
@@ -158,7 +160,7 @@ impl Command for PluginDeclaration {
         pipeline_data
     }
 
-    fn is_plugin(&self) -> Option<(&PathBuf, &str, &Option<PathBuf>)> {
-        Some((&self.filename, self.encoding.to_str(), &self.shell))
+    fn is_plugin(&self) -> Option<(&PathBuf, &Option<PathBuf>)> {
+        Some((&self.filename, &self.shell))
     }
 }
diff --git a/crates/nu-plugin/src/plugin/mod.rs b/crates/nu-plugin/src/plugin/mod.rs
index 194617c291..aa82633d62 100644
--- a/crates/nu-plugin/src/plugin/mod.rs
+++ b/crates/nu-plugin/src/plugin/mod.rs
@@ -7,9 +7,9 @@ use crate::protocol::{CallInput, LabeledError, PluginCall, PluginData, PluginRes
 use crate::EncodingType;
 use std::env;
 use std::fmt::Write;
-use std::io::BufReader;
+use std::io::{BufReader, Read, Write as WriteTrait};
 use std::path::{Path, PathBuf};
-use std::process::{Child, Command as CommandSys, Stdio};
+use std::process::{Child, ChildStdout, Command as CommandSys, Stdio};
 
 use nu_protocol::{CustomValue, ShellError, Span};
 use nu_protocol::{Signature, Value};
@@ -116,7 +116,6 @@ pub(crate) fn call_plugin(
 
 pub fn get_signature(
     path: &Path,
-    encoding: &EncodingType,
     shell: &Option<PathBuf>,
     current_envs: &HashMap<String, String>,
 ) -> Result<Vec<Signature>, ShellError> {
@@ -127,32 +126,34 @@ pub fn get_signature(
         ShellError::PluginFailedToLoad(format!("Error spawning child process: {}", err))
     })?;
 
+    let mut stdin_writer = child
+        .stdin
+        .take()
+        .ok_or_else(|| ShellError::PluginFailedToLoad("plugin missing stdin writer".into()))?;
+    let mut stdout_reader = child
+        .stdout
+        .take()
+        .ok_or_else(|| ShellError::PluginFailedToLoad("Plugin missing stdout reader".into()))?;
+    let encoding = get_plugin_encoding(&mut stdout_reader)?;
+
     // Create message to plugin to indicate that signature is required and
     // send call to plugin asking for signature
-    if let Some(mut stdin_writer) = child.stdin.take() {
-        let encoding_clone = encoding.clone();
-        std::thread::spawn(move || {
-            encoding_clone.encode_call(&PluginCall::Signature, &mut stdin_writer)
-        });
-    }
+    let encoding_clone = encoding.clone();
+    std::thread::spawn(move || {
+        encoding_clone.encode_call(&PluginCall::Signature, &mut stdin_writer)
+    });
 
     // deserialize response from plugin to extract the signature
-    let signatures = if let Some(stdout_reader) = &mut child.stdout {
-        let reader = stdout_reader;
-        let mut buf_read = BufReader::with_capacity(OUTPUT_BUFFER_SIZE, reader);
-        let response = encoding.decode_response(&mut buf_read)?;
+    let reader = stdout_reader;
+    let mut buf_read = BufReader::with_capacity(OUTPUT_BUFFER_SIZE, reader);
+    let response = encoding.decode_response(&mut buf_read)?;
 
-        match response {
-            PluginResponse::Signature(sign) => Ok(sign),
-            PluginResponse::Error(err) => Err(err.into()),
-            _ => Err(ShellError::PluginFailedToLoad(
-                "Plugin missing signature".into(),
-            )),
-        }
-    } else {
-        Err(ShellError::PluginFailedToLoad(
-            "Plugin missing stdout reader".into(),
-        ))
+    let signatures = match response {
+        PluginResponse::Signature(sign) => Ok(sign),
+        PluginResponse::Error(err) => Err(err.into()),
+        _ => Err(ShellError::PluginFailedToLoad(
+            "Plugin missing signature".into(),
+        )),
     }?;
 
     match child.wait() {
@@ -196,6 +197,24 @@ pub fn serve_plugin(plugin: &mut impl Plugin, encoder: impl PluginEncoder) {
         std::process::exit(0)
     }
 
+    // tell nushell encoding.
+    //
+    //                         1 byte
+    // encoding format: |  content-length  | content    |
+    {
+        let mut stdout = std::io::stdout();
+        let encoding = encoder.name();
+        let length = encoding.len() as u8;
+        let mut encoding_content: Vec<u8> = encoding.as_bytes().to_vec();
+        encoding_content.insert(0, length);
+        stdout
+            .write_all(&encoding_content)
+            .expect("Failed to tell nushell my encoding");
+        stdout
+            .flush()
+            .expect("Failed to tell nushell my encoding when flushing stdout");
+    }
+
     let mut stdin_buf = BufReader::with_capacity(OUTPUT_BUFFER_SIZE, std::io::stdin());
     let plugin_call = encoder.decode_call(&mut stdin_buf);
 
@@ -332,3 +351,22 @@ fn print_help(plugin: &mut impl Plugin, encoder: impl PluginEncoder) {
 
     println!("{}", help)
 }
+
+pub fn get_plugin_encoding(child_stdout: &mut ChildStdout) -> Result<EncodingType, ShellError> {
+    let mut length_buf = [0u8; 1];
+    child_stdout.read_exact(&mut length_buf).map_err(|e| {
+        ShellError::PluginFailedToLoad(format!("unable to get encoding from plugin: {e}"))
+    })?;
+
+    let mut buf = vec![0u8; length_buf[0] as usize];
+    child_stdout.read_exact(&mut buf).map_err(|e| {
+        ShellError::PluginFailedToLoad(format!("unable to get encoding from plugin: {e}"))
+    })?;
+
+    EncodingType::try_from_bytes(&buf).ok_or_else(|| {
+        let encoding_for_debug = String::from_utf8_lossy(&buf);
+        ShellError::PluginFailedToLoad(format!(
+            "get unsupported plugin encoding: {encoding_for_debug}"
+        ))
+    })
+}
diff --git a/crates/nu-plugin/src/protocol/plugin_custom_value.rs b/crates/nu-plugin/src/protocol/plugin_custom_value.rs
index a85be449e7..dbde579909 100644
--- a/crates/nu-plugin/src/protocol/plugin_custom_value.rs
+++ b/crates/nu-plugin/src/protocol/plugin_custom_value.rs
@@ -3,10 +3,7 @@ use std::path::PathBuf;
 use nu_protocol::{CustomValue, ShellError, Value};
 use serde::Serialize;
 
-use crate::{
-    plugin::{call_plugin, create_command},
-    EncodingType,
-};
+use crate::plugin::{call_plugin, create_command, get_plugin_encoding};
 
 use super::{PluginCall, PluginData, PluginResponse};
 
@@ -32,8 +29,6 @@ pub struct PluginCustomValue {
     #[serde(skip)]
     pub shell: Option<PathBuf>,
     #[serde(skip)]
-    pub encoding: EncodingType,
-    #[serde(skip)]
     pub source: String,
 }
 
@@ -72,8 +67,19 @@ impl CustomValue for PluginCustomValue {
             data: self.data.clone(),
             span,
         });
+        let encoding = {
+            let stdout_reader = match &mut child.stdout {
+                Some(out) => out,
+                None => {
+                    return Err(ShellError::PluginFailedToLoad(
+                        "Plugin missing stdout reader".into(),
+                    ))
+                }
+            };
+            get_plugin_encoding(stdout_reader)?
+        };
 
-        let response = call_plugin(&mut child, plugin_call, &self.encoding, span).map_err(|err| {
+        let response = call_plugin(&mut child, plugin_call, &encoding, span).map_err(|err| {
             ShellError::GenericError(
                 format!(
                     "Unable to decode call for {} to get base value",
diff --git a/crates/nu-plugin/src/serializers/json.rs b/crates/nu-plugin/src/serializers/json.rs
index be90100f15..6d77e11c19 100644
--- a/crates/nu-plugin/src/serializers/json.rs
+++ b/crates/nu-plugin/src/serializers/json.rs
@@ -7,7 +7,7 @@ pub struct JsonSerializer;
 
 impl PluginEncoder for JsonSerializer {
     fn name(&self) -> &str {
-        "Json Serializer"
+        "json"
     }
 
     fn encode_call(
diff --git a/crates/nu-plugin/src/serializers/msgpack.rs b/crates/nu-plugin/src/serializers/msgpack.rs
index 733561877a..20e6df5920 100644
--- a/crates/nu-plugin/src/serializers/msgpack.rs
+++ b/crates/nu-plugin/src/serializers/msgpack.rs
@@ -6,7 +6,7 @@ pub struct MsgPackSerializer;
 
 impl PluginEncoder for MsgPackSerializer {
     fn name(&self) -> &str {
-        "MsgPack Serializer"
+        "msgpack"
     }
 
     fn encode_call(
@@ -23,7 +23,7 @@ impl PluginEncoder for MsgPackSerializer {
         reader: &mut impl std::io::BufRead,
     ) -> Result<crate::protocol::PluginCall, nu_protocol::ShellError> {
         rmp_serde::from_read(reader)
-            .map_err(|err| ShellError::PluginFailedToEncode(err.to_string()))
+            .map_err(|err| ShellError::PluginFailedToDecode(err.to_string()))
     }
 
     fn encode_response(
@@ -40,7 +40,7 @@ impl PluginEncoder for MsgPackSerializer {
         reader: &mut impl std::io::BufRead,
     ) -> Result<PluginResponse, ShellError> {
         rmp_serde::from_read(reader)
-            .map_err(|err| ShellError::PluginFailedToEncode(err.to_string()))
+            .map_err(|err| ShellError::PluginFailedToDecode(err.to_string()))
     }
 }
 
diff --git a/crates/nu-protocol/src/engine/command.rs b/crates/nu-protocol/src/engine/command.rs
index 7d9d0242e6..0fa1e22799 100644
--- a/crates/nu-protocol/src/engine/command.rs
+++ b/crates/nu-protocol/src/engine/command.rs
@@ -57,9 +57,8 @@ pub trait Command: Send + Sync + CommandClone {
         false
     }
 
-    // Is a plugin command (returns plugin's path, encoding and type of shell
-    // if the declaration is a plugin)
-    fn is_plugin(&self) -> Option<(&PathBuf, &str, &Option<PathBuf>)> {
+    // Is a plugin command (returns plugin's path, type of shell if the declaration is a plugin)
+    fn is_plugin(&self) -> Option<(&PathBuf, &Option<PathBuf>)> {
         None
     }
 
diff --git a/crates/nu-protocol/src/engine/engine_state.rs b/crates/nu-protocol/src/engine/engine_state.rs
index 240d06ef4a..ff5e73ceeb 100644
--- a/crates/nu-protocol/src/engine/engine_state.rs
+++ b/crates/nu-protocol/src/engine/engine_state.rs
@@ -366,8 +366,7 @@ impl EngineState {
                 self.plugin_decls().try_for_each(|decl| {
                     // A successful plugin registration already includes the plugin filename
                     // No need to check the None option
-                    let (path, encoding, shell) =
-                        decl.is_plugin().expect("plugin should have file name");
+                    let (path, shell) = decl.is_plugin().expect("plugin should have file name");
                     let mut file_name = path
                         .to_str()
                         .expect("path was checked during registration as a str")
@@ -394,14 +393,10 @@ impl EngineState {
                                 None => "".into(),
                             };
 
-                            // Each signature is stored in the plugin file with the required
-                            // encoding, shell and signature
+                            // Each signature is stored in the plugin file with the shell and signature
                             // This information will be used when loading the plugin
                             // information when nushell starts
-                            format!(
-                                "register {} -e {} {} {}\n\n",
-                                file_name, encoding, shell_str, signature
-                            )
+                            format!("register {} {} {}\n\n", file_name, shell_str, signature)
                         })
                         .map_err(|err| ShellError::PluginFailedToLoad(err.to_string()))
                         .and_then(|line| {
diff --git a/crates/nu-test-support/src/macros.rs b/crates/nu-test-support/src/macros.rs
index 4851baf6a7..593202c998 100644
--- a/crates/nu-test-support/src/macros.rs
+++ b/crates/nu-test-support/src/macros.rs
@@ -225,11 +225,11 @@ macro_rules! with_exe {
 
 #[macro_export]
 macro_rules! nu_with_plugins {
-    (cwd: $cwd:expr, plugins: [$(($format:expr, $plugin_name:expr)),+$(,)?], $command:expr) => {{
-        nu_with_plugins!($cwd, [$(($format, $plugin_name)),+], $command)
+    (cwd: $cwd:expr, plugins: [$(($plugin_name:expr)),+$(,)?], $command:expr) => {{
+        nu_with_plugins!($cwd, [$(("", $plugin_name)),+], $command)
     }};
-    (cwd: $cwd:expr, plugin: ($format:expr, $plugin_name:expr), $command:expr) => {{
-        nu_with_plugins!($cwd, [($format, $plugin_name)], $command)
+    (cwd: $cwd:expr, plugin: ($plugin_name:expr), $command:expr) => {{
+        nu_with_plugins!($cwd, [("", $plugin_name)], $command)
     }};
 
     ($cwd:expr, [$(($format:expr, $plugin_name:expr)),+$(,)?], $command:expr) => {{
@@ -254,8 +254,10 @@ macro_rules! nu_with_plugins {
 
         $($crate::commands::ensure_binary_present($plugin_name);)+
 
+        // TODO: the `$format` is a dummy empty string, but `plugin_name` is repeatable
+        // just keep it here for now.  Need to find a way to remove it.
         let registrations = format!(
-            concat!($(concat!("register -e ", $format, " {};")),+),
+            concat!($(concat!("register ", $format, " {};")),+),
             $(
                 nu_path::canonicalize_with(with_exe!($plugin_name), &test_bins)
                     .unwrap_or_else(|e| {
diff --git a/tests/plugins/core_inc.rs b/tests/plugins/core_inc.rs
index 5811f24865..61f105fd57 100644
--- a/tests/plugins/core_inc.rs
+++ b/tests/plugins/core_inc.rs
@@ -6,7 +6,7 @@ use nu_test_support::playground::Playground;
 fn chooses_highest_increment_if_given_more_than_one() {
     let actual = nu_with_plugins!(
         cwd: "tests/fixtures/formats",
-        plugin: ("json", "nu_plugin_inc"),
+        plugin: ("nu_plugin_inc"),
         "open cargo_sample.toml | first 1 | inc package.version --major --minor | get package.version"
     );
 
@@ -14,7 +14,7 @@ fn chooses_highest_increment_if_given_more_than_one() {
 
     let actual = nu_with_plugins!(
         cwd: "tests/fixtures/formats",
-        plugin: ("json", "nu_plugin_inc"),
+        plugin: ("nu_plugin_inc"),
         // Regardless of order of arguments
         "open cargo_sample.toml | first 1 | inc package.version --minor --major | get package.version"
     );
@@ -35,7 +35,7 @@ fn by_one_with_field_passed() {
 
         let actual = nu_with_plugins!(
             cwd: dirs.test(),
-            plugin: ("json", "nu_plugin_inc"),
+            plugin: ("nu_plugin_inc"),
             "open sample.toml | inc package.edition | get package.edition"
         );
 
@@ -56,7 +56,7 @@ fn by_one_with_no_field_passed() {
 
         let actual = nu_with_plugins!(
             cwd: dirs.test(),
-            plugin: ("json", "nu_plugin_inc"),
+            plugin: ("nu_plugin_inc"),
             "open sample.toml | get package.contributors | inc"
         );
 
@@ -77,7 +77,7 @@ fn semversion_major_inc() {
 
         let actual = nu_with_plugins!(
             cwd: dirs.test(),
-            plugin: ("json", "nu_plugin_inc"),
+            plugin: ("nu_plugin_inc"),
             "open sample.toml | inc package.version -M | get package.version"
         );
 
@@ -98,7 +98,7 @@ fn semversion_minor_inc() {
 
         let actual = nu_with_plugins!(
             cwd: dirs.test(),
-            plugin: ("json", "nu_plugin_inc"),
+            plugin: ("nu_plugin_inc"),
             "open sample.toml | inc package.version --minor | get package.version"
         );
 
@@ -119,7 +119,7 @@ fn semversion_patch_inc() {
 
         let actual = nu_with_plugins!(
             cwd: dirs.test(),
-            plugin: ("json", "nu_plugin_inc"),
+            plugin: ("nu_plugin_inc"),
             "open sample.toml | inc package.version --patch | get package.version"
         );
 
@@ -140,7 +140,7 @@ fn semversion_without_passing_field() {
 
         let actual = nu_with_plugins!(
             cwd: dirs.test(),
-            plugin: ("json", "nu_plugin_inc"),
+            plugin: ("nu_plugin_inc"),
             "open sample.toml | get package.version | inc --patch"
         );
 
diff --git a/tests/plugins/custom_values.rs b/tests/plugins/custom_values.rs
index 946df2e6b8..6493d4f7e9 100644
--- a/tests/plugins/custom_values.rs
+++ b/tests/plugins/custom_values.rs
@@ -4,7 +4,7 @@ use nu_test_support::nu_with_plugins;
 fn can_get_custom_value_from_plugin_and_instantly_collapse_it() {
     let actual = nu_with_plugins!(
         cwd: "tests",
-        plugin: ("msgpack", "nu_plugin_custom_values"),
+        plugin: ("nu_plugin_custom_values"),
         "custom-value generate"
     );
 
@@ -15,7 +15,7 @@ fn can_get_custom_value_from_plugin_and_instantly_collapse_it() {
 fn can_get_custom_value_from_plugin_and_pass_it_over() {
     let actual = nu_with_plugins!(
         cwd: "tests",
-        plugin: ("msgpack", "nu_plugin_custom_values"),
+        plugin: ("nu_plugin_custom_values"),
         "custom-value generate | custom-value update"
     );
 
@@ -29,7 +29,7 @@ fn can_get_custom_value_from_plugin_and_pass_it_over() {
 fn can_generate_and_updated_multiple_types_of_custom_values() {
     let actual = nu_with_plugins!(
         cwd: "tests",
-        plugin: ("msgpack", "nu_plugin_custom_values"),
+        plugin: ("nu_plugin_custom_values"),
         "custom-value generate2 | custom-value update"
     );
 
@@ -43,7 +43,7 @@ fn can_generate_and_updated_multiple_types_of_custom_values() {
 fn can_get_describe_plugin_custom_values() {
     let actual = nu_with_plugins!(
         cwd: "tests",
-        plugin: ("msgpack", "nu_plugin_custom_values"),
+        plugin: ("nu_plugin_custom_values"),
         "custom-value generate | describe"
     );
 
@@ -58,7 +58,7 @@ fn can_get_describe_plugin_custom_values() {
 fn fails_if_passing_engine_custom_values_to_plugins() {
     let actual = nu_with_plugins!(
         cwd: "tests/fixtures/formats",
-        plugin: ("msgpack", "nu_plugin_custom_values"),
+        plugin: ("nu_plugin_custom_values"),
         "open-db sample.db | custom-value update"
     );
 
@@ -72,8 +72,8 @@ fn fails_if_passing_custom_values_across_plugins() {
     let actual = nu_with_plugins!(
         cwd: "tests",
         plugins: [
-            ("msgpack", "nu_plugin_custom_values"),
-            ("json", "nu_plugin_inc")
+            ("nu_plugin_custom_values"),
+            ("nu_plugin_inc")
         ],
         "custom-value generate | inc --major"
     );