diff --git a/firefox-focus-monitor.py b/firefox-focus-monitor.py
old mode 100644
new mode 100755
index d2a2d42..659b893
--- a/firefox-focus-monitor.py
+++ b/firefox-focus-monitor.py
@@ -1,2 +1,3 @@
+#!/usr/bin/env python3
 """
 Utility to selectively disable keypresses to specific windows.