diff --git a/common/flatpak-run.c b/common/flatpak-run.c
index 141a1cd3..2ab7b25f 100644
--- a/common/flatpak-run.c
+++ b/common/flatpak-run.c
@@ -176,7 +176,7 @@ write_xauth (char *number, FILE *output)
           local_xa = *xa;
           if (local_xa.number)
             {
-              local_xa.number = "99";
+              local_xa.number = (char *) "99";
               local_xa.number_length = 2;
             }