diff --git a/src/chain.h b/src/chain.h
index b72fe9cab..67c63cf09 100644
--- a/src/chain.h
+++ b/src/chain.h
@@ -515,7 +515,7 @@ public:
         if(phashBlock == NULL) {
             auto header = this->GetBlockHeader();
             auto blockhash = header.GetHash();
-            fprintf(stderr, "GetBlockHash: phashBlock NULL at height %d, returning blockhash=%s instead\n", this->GetHeight(), blockhash.ToString() );
+            fprintf(stderr, "GetBlockHash: phashBlock NULL at height %d, returning blockhash=%s instead\n", this->GetHeight(), blockhash.ToString().c_str() );
             // assert(phashBlock);
             return blockhash;
         }