diff --git a/util/logging.cc b/util/logging.cc
index c54ea1cdc..98d96b82b 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", static_cast<unsigned long long>(num));
+  snprintf(buf, sizeof(buf), "%" PRIu64, num);
   str->append(buf);
 }