diff --git a/docs/source/extensions/pdf_button.py b/docs/source/extensions/pdf_button.py
index 0b4d3d6..ec6d7d0 100644
--- a/docs/source/extensions/pdf_button.py
+++ b/docs/source/extensions/pdf_button.py
@@ -20,7 +20,7 @@ def run(self):
         # Check if explicitly marked as a local build
         
         on_gitlab = os.environ.get('GITLAB_CI') == 'true'
-        on_github = os.environ.get('ON_GITHUB') == 'true' # custom environment variable
+        on_github = os.environ.get('GITHUB_ACTIONS') == 'true' # custom environment variable
 
         if on_gitlab:
             pdf_path = f'/_static/{pdf_filename}'