diff --git a/.github/workflows/code_checks.yml b/.github/workflows/code_checks.yml
index 065271f877..d3ce8b644c 100644
--- a/.github/workflows/code_checks.yml
+++ b/.github/workflows/code_checks.yml
@@ -87,8 +87,8 @@ jobs:
         run: |
             git fetch --depth=1 origin master
             if git diff origin/master \
-               ':!.github/workflows/code_checks.yml' \
-               | grep -E '^\+.*(wxOVERRIDE|wxNOEXCEPT|[^_@]NULL)'; then
+               ':**.h' ':**.cpp' \
+               | grep -E '^\+.*(wxOVERRIDE|wxNOEXCEPT|[^"_@]NULL[^"_])'; then
               echo "::error ::Please use C++11 equivalents of the deprecated macros in the new code."
               exit 1
             fi