diff --git a/link.cpp b/link.cpp
index 00462ca..19f55a3 100644
--- a/link.cpp
+++ b/link.cpp
@@ -411,7 +411,7 @@ void simplify() {
  */
 
 std::string &upper_case(std::string &s) {
-	std::transform(s.begin(), s.end(), s.begin(), std::toupper);
+	std::transform(s.begin(), s.end(), s.begin(), toupper);
 	return s;
 }