diff --git a/test/suite/batpipe.sh b/test/suite/batpipe.sh
index 4a4776c..d942b41 100644
--- a/test/suite/batpipe.sh
+++ b/test/suite/batpipe.sh
@@ -12,9 +12,18 @@ test:detected_bash_shell() {
 
 test:detected_fish_shell() {
 	description "Test it can detect a fish shell."
-	
-	output="$(SHELL="fish" fish --login -c "$(batpipe_path)")"
-	grep '^set -x' <<< "$output" >/dev/null || fail "Detected the wrong shell for fish."
+
+	# Note: We don't use bash's `-c` option when testing with a fake fish shell.
+	# Bash `-c` will automatically exec() into the last process, which loses the
+	# argv0 we intentionally named after a different shell.
+
+	# Test detection via `*sh -l` parent process.
+	output="$(printf "%q" "$(batpipe_path)" | fish -l)"
+	grep '^set -x' <<< "$output" >/dev/null || fail 'Detected wrong shell when checking parent process args.'
+
+	# Test detection via hypen-prefixed parent process.
+	output="$(printf "%q" "$(batpipe_path)" | SHIM_ARGV0='-fish' fish)"
+	grep '^set -x' <<< "$output" >/dev/null || fail 'Detected wrong shell when checking parent process.'
 }
 
 test:viewer_gzip() {