diff --git a/git-open b/git-open
index efce3de..6adb949 100755
--- a/git-open
+++ b/git-open
@@ -259,7 +259,7 @@ elif [[ $remote_ref != "master" || "$file" ]]; then
 fi
 
 if [ "$file" ]; then
-    absfile=$(git ls-tree --full-name --name-only $branch $file)
+    absfile=$(git ls-tree --full-name --name-only "$branch" "$file")
     if [[ -z "$absfile" ]]; then
       echo "File $file is not in repository" 1>&2
       exit 1