Fix clang -Weverything
diff --git a/test/unittest/simdtest.cpp b/test/unittest/simdtest.cpp
index c8f4587..4407c25 100644
--- a/test/unittest/simdtest.cpp
+++ b/test/unittest/simdtest.cpp
@@ -41,7 +41,7 @@
 
 template <typename StreamType>
 void TestSkipWhitespace() {
-    for (int step = 1; step < 32; step++) {
+    for (size_t step = 1; step < 32; step++) {
         char buffer[1025];
         for (size_t i = 0; i < 1024; i++)
             buffer[i] = " \t\r\n"[i % 4];