diff --git a/crates/nu-command/src/core_commands/def_env.rs b/crates/nu-command/src/core_commands/def_env.rs
index e880d1d89d..14c66022be 100644
--- a/crates/nu-command/src/core_commands/def_env.rs
+++ b/crates/nu-command/src/core_commands/def_env.rs
@@ -28,7 +28,33 @@ impl Command for DefEnv {
 
     fn extra_usage(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
-  https://www.nushell.sh/book/thinking_in_nushell.html"#
+  https://www.nushell.sh/book/thinking_in_nushell.html
+
+=== EXTRA NOTE ===
+All blocks are scoped, including variable definition and environment variable changes.
+
+Because of this, the following doesn't work:
+
+def-env cd_with_fallback [arg = ""] {
+    let fall_back_path = "/tmp"
+    if $arg != "" {
+        cd $arg
+    } else {
+        cd $fall_back_path
+    }
+}
+
+Instead, you have to use cd in the top level scope:
+
+def-env cd_with_fallback [arg = ""] {
+    let fall_back_path = "/tmp"
+    let path = if $arg != "" {
+        $arg
+    } else {
+        $fall_back_path
+    }
+    cd $path
+}"#
     }
 
     fn is_parser_keyword(&self) -> bool {
diff --git a/crates/nu-command/src/core_commands/export_def_env.rs b/crates/nu-command/src/core_commands/export_def_env.rs
index 65de978865..b08311b0c6 100644
--- a/crates/nu-command/src/core_commands/export_def_env.rs
+++ b/crates/nu-command/src/core_commands/export_def_env.rs
@@ -28,7 +28,33 @@ impl Command for ExportDefEnv {
 
     fn extra_usage(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
-  https://www.nushell.sh/book/thinking_in_nushell.html"#
+  https://www.nushell.sh/book/thinking_in_nushell.html
+
+=== EXTRA NOTE ===
+All blocks are scoped, including variable definition and environment variable changes.
+
+Because of this, the following doesn't work:
+
+export def-env cd_with_fallback [arg = ""] {
+    let fall_back_path = "/tmp"
+    if $arg != "" {
+        cd $arg
+    } else {
+        cd $fall_back_path
+    }
+}
+
+Instead, you have to use cd in the top level scope:
+
+export def-env cd_with_fallback [arg = ""] {
+    let fall_back_path = "/tmp"
+    let path = if $arg != "" {
+        $arg
+    } else {
+        $fall_back_path
+    }
+    cd $path
+}"#
     }
 
     fn is_parser_keyword(&self) -> bool {