diff --git a/wpa_supplicant/interworking.c b/wpa_supplicant/interworking.c
index 0261bb7b8..d8e9c95a7 100644
--- a/wpa_supplicant/interworking.c
+++ b/wpa_supplicant/interworking.c
@@ -2262,7 +2262,7 @@ int interworking_home_sp_cred(struct wpa_supplicant *wpa_s,
 			realm++;
 		wpa_msg(wpa_s, MSG_DEBUG,
 			"Interworking: Search for match with SIM/USIM domain %s",
-			realm);
+			realm ? realm : "[NULL]");
 		if (realm &&
 		    domain_name_list_contains(domain_names, realm, 1))
 			return 1;