diff --git a/src/devices/wwan/nm-modem-broadband.c b/src/devices/wwan/nm-modem-broadband.c
index 3fd94586a9..40cf32c772 100644
--- a/src/devices/wwan/nm-modem-broadband.c
+++ b/src/devices/wwan/nm-modem-broadband.c
@@ -66,6 +66,8 @@ translate_mm_error (GError *error)
 {
 	NMDeviceStateReason reason;
 
+	g_return_val_if_fail (error != NULL, NM_DEVICE_STATE_REASON_UNKNOWN);
+
 	if (g_error_matches (error, MM_CONNECTION_ERROR, MM_CONNECTION_ERROR_NO_CARRIER))
 		reason = NM_DEVICE_STATE_REASON_MODEM_NO_CARRIER;
 	else if (g_error_matches (error, MM_CONNECTION_ERROR, MM_CONNECTION_ERROR_NO_DIALTONE))
diff --git a/src/nm-manager.c b/src/nm-manager.c
index 64c31c89dc..52a01895e8 100644
--- a/src/nm-manager.c
+++ b/src/nm-manager.c
@@ -3081,6 +3081,7 @@ _activation_auth_done (NMActiveConnection *active,
 			                         error_desc);
 	}
 
+	g_assert (error);
 	dbus_g_method_return_error (context, error);
 	_internal_activation_failed (self, active, error->message);
 	g_object_unref (active);
@@ -3227,6 +3228,7 @@ activation_add_done (NMSettings *self,
 		error = local;
 	}
 
+	g_assert (error);
 	_internal_activation_failed (info->manager, info->active, error->message);
 	dbus_g_method_return_error (context, error);
 	g_clear_error (&local);