diff --git a/tools/build-all-docker-images b/tools/build-all-docker-images
index 0f2ba03cb6..5f016f72c4 100755
--- a/tools/build-all-docker-images
+++ b/tools/build-all-docker-images
@@ -80,7 +80,7 @@ function init_image {
 
 function process_image {
     local image=$1
-    if [ -n ${dependency[$image]} ]; then
+    if [ -n "${dependency[$image]}" ]; then
         process_image ${dependency[$image]}
     fi
     if requires_build $image; then