diff --git a/src/gprs.c b/src/gprs.c
index d5f9dc99..506baf1d 100644
--- a/src/gprs.c
+++ b/src/gprs.c
@@ -208,6 +208,9 @@ static DBusMessage *pri_set_apn(struct pri_context *ctx, DBusConnection *conn,
 	if (g_str_equal(apn, ctx->context.apn))
 		return dbus_message_new_method_return(msg);
 
+	if (is_valid_apn(apn) == FALSE)
+		return __ofono_error_invalid_format(msg);
+
 	strcpy(ctx->context.apn, apn);
 
 	g_dbus_send_reply(conn, msg, DBUS_TYPE_INVALID);