diff --git a/.github/workflows/check_metadata.yml b/.github/workflows/check_metadata.yml
index bff3ad3..086409e 100644
--- a/.github/workflows/check_metadata.yml
+++ b/.github/workflows/check_metadata.yml
@@ -41,7 +41,7 @@ jobs:
 
           git status
           # array of accepted copyright strings
-          accepted_cr=("GNU GPL v2+" "CC BY-SA 4.0")
+          accepted_cr=("GNU GPL v2+|CC BY-SA 4.0|CC0")
           # cycle through the changed image files, make sure they have the right fields
           for file in "${image_files[@]}"; do
             # check -Artist tag, fail if missing
@@ -60,7 +60,7 @@ jobs:
               echo "no Copyright EXIF tag in $file"
               exit 1
             # elif [[ ( "$copyright" != ${accepted_cr[0]} ) && ( "$copyright" != ${accepted_cr[1]}) ]] ; then
-            elif [[ ! " ${accepted_cr[*]} " =~ " ${copyright} " ]]; then
+            elif [[ ! "|${accepted_cr[*]}|" =~ "|${copyright}|" ]]; then
               echo "$copyright is not an accepted license"
               exit 1
             else