diff --git a/oh-my-zsh.sh b/oh-my-zsh.sh
index 6b2662d5e..c3fae6efb 100644
--- a/oh-my-zsh.sh
+++ b/oh-my-zsh.sh
@@ -32,8 +32,8 @@ fi
 is_plugin() {
   local base_dir=$1
   local name=$2
-  test -f $base_dir/plugins/$name/$name.plugin.zsh \
-    || test -f $base_dir/plugins/$name/_$name
+  builtin test -f $base_dir/plugins/$name/$name.plugin.zsh \
+    || builtin test -f $base_dir/plugins/$name/_$name
 }
 
 # Add all defined plugins to fpath. This must be done