diff --git a/contrib/ChangeLog b/contrib/ChangeLog
index 4063452cc8ff..2c45f0ae4719 100644
--- a/contrib/ChangeLog
+++ b/contrib/ChangeLog
@@ -1,3 +1,8 @@
+2015-09-11  Markus Trippelsdorf  <markus@trippelsdorf.de>
+
+	* download_prerequisites: Make sure that script is run from
+	top level source directory.
+
 2015-07-16  Release Manager
 
 	* GCC 5.2.0 released.
diff --git a/contrib/download_prerequisites b/contrib/download_prerequisites
index de0e7c41847d..69403301b813 100755
--- a/contrib/download_prerequisites
+++ b/contrib/download_prerequisites
@@ -24,6 +24,11 @@
 # be downloaded.
 GRAPHITE_LOOP_OPT=yes
 
+if [ ! -e gcc/BASE-VER ] ; then
+	echo "You must run this script in the top level GCC source directory."
+	exit 1
+fi
+
 # Necessary to build GCC.
 MPFR=mpfr-2.4.2
 GMP=gmp-4.3.2