diff --git a/src/chain.h b/src/chain.h
index 03d3b3be2..46136df99 100644
--- a/src/chain.h
+++ b/src/chain.h
@@ -512,7 +512,10 @@ public:
 
     uint256 GetBlockHash() const
     {
-        assert(phashBlock);
+        if(phashBlock == NULL) {
+            fprintf(stderr, "GetBlockHash: phashBlock NULL at height %d\n", this->GetHeight());
+            assert(phashBlock);
+        }
         return *phashBlock;
     }