diff --git a/compression/stats.cc b/compression/stats.cc
index 2013422..8e66119 100644
--- a/compression/stats.cc
+++ b/compression/stats.cc
@@ -114,7 +114,7 @@ std::string Stats::ToString(int exclude) const {
     pos += ret;
   }
 
-  HWY_ASSERT(pos < sizeof(buf));
+  HWY_ASSERT(pos < static_cast<int>(sizeof(buf)));
   return buf;
 }