diff --git a/src/auth/mech-gssapi.c b/src/auth/mech-gssapi.c
index f29e48da88..966273d388 100644
--- a/src/auth/mech-gssapi.c
+++ b/src/auth/mech-gssapi.c
@@ -735,7 +735,7 @@ mech_gssapi_auth_free(struct auth_request *request)
 const struct mech_module mech_gssapi = {
 	"GSSAPI",
 
-	.flags = 0,
+	.flags = MECH_SEC_ALLOW_NULS,
 	.passdb_need = MECH_PASSDB_NEED_NOTHING,
 
 	mech_gssapi_auth_new,