diff --git a/src/main.cpp b/src/main.cpp
index be9d34e40..578cc25ea 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3235,7 +3235,7 @@ bool AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, CBloc
         if (mi == mapBlockIndex.end())
             return state.DoS(10, error("%s: prev block not found", __func__), 0, "bad-prevblk");
         pindexPrev = (*mi).second;
-        if (pindexPrev->nStatus & BLOCK_FAILED_MASK)
+        if (pindexPrev == 0 || (pindexPrev->nStatus & BLOCK_FAILED_MASK) )
             return state.DoS(100, error("%s: prev block invalid", __func__), REJECT_INVALID, "bad-prevblk");
     }
     if (!ContextualCheckBlockHeader(block, state, pindexPrev))