diff --git a/src/gallium/drivers/r600/sb/sb_gcm.cpp b/src/gallium/drivers/r600/sb/sb_gcm.cpp
index bccb671..39b6cdd 100644
--- a/src/gallium/drivers/r600/sb/sb_gcm.cpp
+++ b/src/gallium/drivers/r600/sb/sb_gcm.cpp
@@ -577,7 +577,7 @@ void gcm::bu_find_best_bb(node *n, op_info &oi) {
 	// For now just check if top_bb's loop_level is higher than of
 	// current bb and abort the search for better bb in such case,
 	// but this problem may require more complete (and more expensive) fix
-	if (top_bb->loop_level <= best_bb->loop_level) {
+	if ((top_bb) && (top_bb->loop_level <= best_bb->loop_level)) {
 		while (c && c != top_bb) {
 
 			if (c->prev) {