diff --git a/src/out b/src/out
index 081b965..a6db122 100755
--- a/src/out
+++ b/src/out
@@ -17,8 +17,8 @@ if [ -n "$additional_tags" ]; then
     if ! [ -e "$additional_tags" ]; then
         fail "additional_tags specified, but doesn't exist"
     fi
-    tr ' \n\t' '\n\n\n' | grep -v '^$' | while read -r tag; do
-        crane tag "$REPOSITORY:@$(cat "$image_refs_file)" "$tag"
+    tr '[:space:]' '\n' | grep -v '^$' | while read -r tag; do
+        crane tag "$REPOSITORY:@$(cat "$image_refs_file")" "$tag"
     done
 fi