diff --git a/tests/test-highlighting.zsh b/tests/test-highlighting.zsh
index 74ccc95..c30d571 100755
--- a/tests/test-highlighting.zsh
+++ b/tests/test-highlighting.zsh
@@ -144,7 +144,7 @@ run_test_internal() {
     }
 
     # Check the data declares $PREBUFFER or $BUFFER.
-    [[ -z $PREBUFFER && -z $BUFFER ]] && { echo >&2 "Bail out! On ${(qq)1}: Either 'PREBUFFER' or 'BUFFER' must be declared and non-blank"; return ${RETURN:=1}; }
+    [[ -z $PREBUFFER && -z $BUFFER ]] && { echo >&2 "Bail out! On ${(qq)ARG}: Either 'PREBUFFER' or 'BUFFER' must be declared and non-blank"; return ${RETURN:=1}; }
 
     # Set sane defaults for ZLE variables
     : ${CURSOR=$#BUFFER} ${PENDING=0} ${WIDGET=z-sy-h-test-harness-test-widget}