diff --git a/libethereum/Client.h b/libethereum/Client.h
index 415e4d126..3bf2015c4 100644
--- a/libethereum/Client.h
+++ b/libethereum/Client.h
@@ -309,7 +309,7 @@ class Client : public ClientBase, protected Worker {
     std::string getHistoricNodeIndex( unsigned _idx ) const {
         return chainParams()
             .sChain.nodeGroups.at( historicGroupIndex )
-            .nodes[_idx]
+            .nodes.at( _idx )
             .schainIndex.str();
     }