diff --git a/src/benchmark.cpp b/src/benchmark.cpp
index c31609bb..b9cd4058 100644
--- a/src/benchmark.cpp
+++ b/src/benchmark.cpp
@@ -85,6 +85,7 @@ void benchmark(istringstream& is) {
 
   if (fenFile != "default")
   {
+      fens.clear();
       string fen;
       ifstream file(fenFile.c_str());