diff --git a/src/main.cpp b/src/main.cpp
index 20f28d46a..8dcd3cc10 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3170,6 +3170,11 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
         //fprintf(stderr,"checkblock failure in connectblock futureblock.%d\n",futureblock);
         return false;
     }
+    if ( fCheckPOW != 0 && pindex->nTime > 1548979200 && !ContextualCheckBlock(block, state, pindex->pprev) ) // activate check Feb 1, 2019
+    {
+        fprintf(stderr,"ContextualCheckBlock failed ht.%d\n",(int32_t)pindex->GetHeight());
+        return false;
+    }
 
     // verify that the view's current state corresponds to the previous block
     uint256 hashPrevBlock = pindex->pprev == NULL ? uint256() : pindex->pprev->GetBlockHash();