diff --git a/ffbuild/libversion.sh b/ffbuild/libversion.sh
index a94ab58057..ecaa90cde6 100755
--- a/ffbuild/libversion.sh
+++ b/ffbuild/libversion.sh
@@ -1,3 +1,4 @@
+#!/bin/sh
 toupper(){
     echo "$@" | tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
 }