diff --git a/intern/cycles/bvh/bvh.cpp b/intern/cycles/bvh/bvh.cpp
index 500b07f755b..f11b3c4c0bc 100644
--- a/intern/cycles/bvh/bvh.cpp
+++ b/intern/cycles/bvh/bvh.cpp
@@ -30,6 +30,7 @@
 #include "util_foreach.h"
 #include "util_map.h"
 #include "util_progress.h"
+#include "util_system.h"
 #include "util_types.h"
 
 CCL_NAMESPACE_BEGIN
@@ -71,6 +72,7 @@ BVH *BVH::create(const BVHParams& params, const vector<Object*>& objects)
 
 bool BVH::cache_read(CacheData& key)
 {
+	key.add(system_cpu_bits());
 	key.add(&params, sizeof(params));
 
 	foreach(Object *ob, objects) {
diff --git a/intern/cycles/util/util_cache.h b/intern/cycles/util/util_cache.h
index e8f111a5397..deff05fff16 100644
--- a/intern/cycles/util/util_cache.h
+++ b/intern/cycles/util/util_cache.h
@@ -72,7 +72,7 @@ public:
 		buffers.push_back(buffer);
 	}
 
-	void add(void *data, size_t size)
+	void add(const void *data, size_t size)
 	{
 		if(size) {
 			CacheBuffer buffer(data, size);
@@ -80,19 +80,19 @@ public:
 		}
 	}
 
-	void add(int& data)
+	void add(const int& data)
 	{
 		CacheBuffer buffer(&data, sizeof(int));
 		buffers.push_back(buffer);
 	}
 
-	void add(float& data)
+	void add(const float& data)
 	{
 		CacheBuffer buffer(&data, sizeof(float));
 		buffers.push_back(buffer);
 	}
 
-	void add(size_t& data)
+	void add(const size_t& data)
 	{
 		CacheBuffer buffer(&data, sizeof(size_t));
 		buffers.push_back(buffer);