diff --git a/src/main.cpp b/src/main.cpp
index 182983673..5090b94fa 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3033,7 +3033,7 @@ bool InvalidateBlock(CValidationState& state, CBlockIndex *pindex) {
     // The resulting new best tip may not be in setBlockIndexCandidates anymore, so
     // add it again.
     BlockMap::iterator it = mapBlockIndex.begin();
-    while (it != mapBlockIndex.end()) {
+    while (it != mapBlockIndex.end() && it->second != 0 ) {
         if (it->second->IsValid(BLOCK_VALID_TRANSACTIONS) && it->second->nChainTx && !setBlockIndexCandidates.value_comp()(it->second, chainActive.Tip())) {
             setBlockIndexCandidates.insert(it->second);
         }