diff --git a/test/perftest/rapidjsontest.cpp b/test/perftest/rapidjsontest.cpp
index dd8bc30..7c58077 100644
--- a/test/perftest/rapidjsontest.cpp
+++ b/test/perftest/rapidjsontest.cpp
@@ -242,7 +242,7 @@ TEST_F(RapidJson, PrettyWriter_StringBuffer) {
 TEST_F(RapidJson, internal_Pow10) {
 	double sum = 0;
 	for (size_t i = 0; i < kTrialCount * kTrialCount; i++)
-		sum += internal::Pow10(i & 255);
+		sum += internal::Pow10(int(i & 255));
 	EXPECT_GT(sum, 0.0);
 }