diff --git a/source/zipchord.ahk b/source/zipchord.ahk
index 707c4fb..68b4920 100644
--- a/source/zipchord.ahk
+++ b/source/zipchord.ahk
@@ -1,4 +1,5 @@
 #NoEnv
+#SingleInstance Force
 SetWorkingDir %A_ScriptDir%
 
 ; ZipChord by Pavel Soukenik