diff --git a/src/mime/backend/mailcap.c b/src/mime/backend/mailcap.c
index 5abe9416..4e7a9224 100644
--- a/src/mime/backend/mailcap.c
+++ b/src/mime/backend/mailcap.c
@@ -301,6 +301,7 @@ parse_optional_fields(struct mailcap_entry *entry, unsigned char *line)
 			for (field = entry->testcommand; *field; field++)
 				if (*field == '%' && *(field+1) == 's') {
 					mem_free(entry->testcommand);
+					entry->testcommand = NULL;
 					return 0;
 				}