diff --git a/util/logging.cc b/util/logging.cc
index 4dfb9a449..1f5b8e2a7 100644
--- a/util/logging.cc
+++ b/util/logging.cc
@@ -45,7 +45,7 @@ int AppendHumanBytes(uint64_t bytes, char* output, int len) {
 
 void AppendNumberTo(std::string* str, uint64_t num) {
   char buf[30];
-  snprintf(buf, sizeof(buf), "%llu", (unsigned long long) num);
+  snprintf(buf, sizeof(buf), "%llu", static_cast(unsigned long long) num);
   str->append(buf);
 }