diff --git a/src/main.cpp b/src/main.cpp
index ba38979ba..5e38a9a4c 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3206,10 +3206,13 @@ bool CheckBlockHeader(int32_t height,CBlockIndex *pindex, const CBlockHeader& bl
         for (i=31; i>=0; i--)
             fprintf(stderr,"%02x",((uint8_t *)&hash)[i]);
         fprintf(stderr," <- CheckBlockHeader\n");
-        hash = chainActive.Tip()->GetBlockHash();
-        for (i=31; i>=0; i--)
-            fprintf(stderr,"%02x",((uint8_t *)&hash)[i]);
-        fprintf(stderr," <- chainTip\n");
+        if ( chainActive.Tip() != 0 )
+        {
+            hash = chainActive.Tip()->GetBlockHash();
+            for (i=31; i>=0; i--)
+                fprintf(stderr,"%02x",((uint8_t *)&hash)[i]);
+            fprintf(stderr," <- chainTip\n");
+        }
     }
     if (blockhdr.GetBlockTime() > GetAdjustedTime() + 60)
         return state.Invalid(error("CheckBlockHeader(): block timestamp too far in the future"),REJECT_INVALID, "time-too-new");