diff --git a/install_modules.sh b/install_modules.sh
index e902cb3a36..9321b9f4bc 100755
--- a/install_modules.sh
+++ b/install_modules.sh
@@ -112,7 +112,7 @@ for MOD in ${!SOURCE_MODULES[*]} ; do
   # fetch the latest refs from the repo
   $GIT_CMD_BASE fetch
   # make sure the correct revision is installed, I have to use rev-list b/c rev-parse does not work with tags
-  if [ `${GIT_CMD_BASE} rev-list HEAD --max-count 1` != `${GIT_CMD_BASE} rev-list ${SOURCE_MODULES[$MOD]} --max-count 1` ]; then
+  if [ `${GIT_CMD_BASE} rev-list HEAD --max-count=1` != `${GIT_CMD_BASE} rev-list ${SOURCE_MODULES[$MOD]} --max-count=1` ]; then
     # checkout correct revision
     $GIT_CMD_BASE checkout ${SOURCE_MODULES[$MOD]}
   fi