diff --git a/bin/brew b/bin/brew
index 86b2973657..2da56eb7a5 100755
--- a/bin/brew
+++ b/bin/brew
@@ -22,7 +22,7 @@ fi
 # Fail fast with concise message when requesting unfiltered environment.
 # This is basically odisabled so can be removed at any major release afterwards
 # and definitely if this is still here in 2023.
-if [ -n "${HOMEBREW_NO_ENV_FILTERING:-}" ]
+if [[ -n "${HOMEBREW_NO_ENV_FILTERING:-}" ]]
 then
   echo "Error: HOMEBREW_NO_ENV_FILTERING was deprecated for over a year and has now been removed (because it breaks many things)!" >&2
   exit 1