diff --git a/mellon_create_metadata.sh b/mellon_create_metadata.sh
index 4009f1d..9c587a6 100644
--- a/mellon_create_metadata.sh
+++ b/mellon_create_metadata.sh
@@ -36,7 +36,7 @@ fi
 HOST="$(echo "$BASEURL" | sed 's#^[a-z]*://\([^/]*\).*#\1#')"
 BASEURL="$(echo "$BASEURL" | sed 's#/$##')"
 
-OUTFILE="$(echo "$ENTITYID" | sed 's/[^A-Za-z.]/_/g' | sed 's/__*/_/g')"
+OUTFILE="$(echo "$ENTITYID" | sed 's/[^0-9A-Za-z.]/_/g' | sed 's/__*/_/g')"
 echo "Output files:"
 echo "Private key:                              $OUTFILE.key"
 echo "Certificate:                              $OUTFILE.cert"