diff --git a/src/sat/bsat/satProof.c b/src/sat/bsat/satProof.c
index 53f60384d..93232f083 100644
--- a/src/sat/bsat/satProof.c
+++ b/src/sat/bsat/satProof.c
@@ -443,6 +443,7 @@ int Sat_ProofReduce( Vec_Set_t * vProof, void * pRoots, int hProofPivot )
         int X = Proof_NodeWordNum(pNode->nEnts);
         hTemp = pNode->Id; pNode->Id = 0;
         assert( hTemp > 1 );
+        assert( hTemp + Proof_NodeWordNum(pNode->nEnts) < (1<<vProof->nPageSize) );
         memmove( Vec_SetEntry(vProof, hTemp), pNode, sizeof(word)*Proof_NodeWordNum(pNode->nEnts) );
         if ( pPivot && pPivot <= pNode )
         {