diff --git a/gc.py b/gc.py
index 37f848f..7d16bb5 100755
--- a/gc.py
+++ b/gc.py
@@ -1,3 +1,5 @@
+#!/usr/bin/env python3
+
 # UTILITY TO CONVERT BETWEEN XYZ AND Z-MATRIX GEOMETRIES
 # Copyright 2017 Robert A Shaw
 #