diff --git a/test/testsupport/perf_test.h b/test/testsupport/perf_test.h
index 95bbf65..02dd1f3 100644
--- a/test/testsupport/perf_test.h
+++ b/test/testsupport/perf_test.h
@@ -47,7 +47,8 @@
 void PrintResultMeanAndError(const std::string& measurement,
                              const std::string& modifier,
                              const std::string& trace,
-                             const std::string& mean_and_error,
+                             const double mean,
+                             const double error,
                              const std::string& units,
                              bool important);