diff --git a/prepare_sources.sh b/prepare_sources.sh
index b0aa8dc7a..e4efa2201 100755
--- a/prepare_sources.sh
+++ b/prepare_sources.sh
@@ -2,6 +2,12 @@
 
 topdir=`pwd`
 
+if [ $# -ne 1 ] 
+then
+	"Error : path to the ndk as parameter."
+	exit 65
+fi
+
 cd submodules/externals/ffmpeg
 if test -z "`git status | grep neon`" ; then
 	echo "Applying patch to ffmpeg"