diff -r ff356949df25 -r 972b9fbb3690 libpurple/protocols.c
--- a/libpurple/protocols.c	Sun Sep 01 02:28:54 2013 +0530
+++ b/libpurple/protocols.c	Sun Sep 01 03:17:23 2013 +0530
@@ -752,6 +752,22 @@
 
 	protocol = g_object_new(protocol_type, NULL);
 
+	if (!PURPLE_IS_PROTOCOL(protocol)) {
+		g_set_error(error, PURPLE_PROTOCOLS_DOMAIN, 0,
+		            _("Protocol type does not inherit PurpleProtocol"));
+
+		g_object_unref(protocol);
+		return NULL;
+	}
+
+	if (!PURPLE_IS_PROTOCOL_INTERFACE(protocol)) {
+		g_set_error(error, PURPLE_PROTOCOLS_DOMAIN, 0,
+		            _("Protocol does not implement PurpleProtocolInterface"));
+
+		g_object_unref(protocol);
+		return NULL;
+	}
+
 	if (!purple_protocol_get_id(protocol)) {
 		g_set_error(error, PURPLE_PROTOCOLS_DOMAIN, 0,
 		            _("Protocol does not provide an ID"));