diff --git a/rebuild.sh b/rebuild.sh
index 350ebb6..d2f5dea 100755
--- a/rebuild.sh
+++ b/rebuild.sh
@@ -1,8 +1,8 @@
 #!/bin/sh
 
 updates_available () {
-    docker pull $1
-    if test "$(docker run -it --rm $1 /bin/sh -c 'apt -qqq update && apt -qq list --upgradable')" != ""; then
+    docker pull "$1"
+    if test "$(docker run -it --rm "$1" /bin/sh -c 'apt -qqq update && apt -qq list --upgradable')" != ""; then
         return 0
     else
         return 1