diff --git a/src/validation.cpp b/src/validation.cpp
index a83737377..3ce7ffc7b 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1739,7 +1739,10 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
                   CCoinsViewCache& view, const CChainParams& chainparams, bool fJustCheck)
 {
     AssertLockHeld(cs_main);
-
+    assert(pindex);
+    // pindex->phashBlock can be null if called by CreateNewBlock/TestBlockValidity
+    assert((pindex->phashBlock == NULL) ||
+           (*pindex->phashBlock == block.GetHash()));
     int64_t nTimeStart = GetTimeMicros();
 
     // Check it again in case a previous version let a bad block in