diff --git a/contrib/ci/pre_test_hook.sh b/contrib/ci/pre_test_hook.sh
index 81f54f317f..ec00e1fdfe 100755
--- a/contrib/ci/pre_test_hook.sh
+++ b/contrib/ci/pre_test_hook.sh
@@ -29,8 +29,8 @@ echo "VOLUME_BACKING_FILE_SIZE=22G" >> $localconf
 echo "CINDER_LVM_TYPE=thin" >> $localconf
 
 # Set DevStack's PYTHON3_VERSION variable if CI scripts specify it
-if ! [[ -z "PYTHON3_VERSION" ]]; then
-echo "PYTHON3_VERSION=$PYTHON3_VERSION" >> $localconf
+if [[ ! -z "$PYTHON3_VERSION" ]]; then
+    echo "PYTHON3_VERSION=$PYTHON3_VERSION" >> $localconf
 fi
 
 # NOTE(mkoderer): switch to keystone v3 by default