diff --git a/clang/include/clang/Analysis/Analyses/ThreadSafetyUtil.h b/clang/include/clang/Analysis/Analyses/ThreadSafetyUtil.h
index 8c987b097c7e..5a7572425c6a 100644
--- a/clang/include/clang/Analysis/Analyses/ThreadSafetyUtil.h
+++ b/clang/include/clang/Analysis/Analyses/ThreadSafetyUtil.h
@@ -24,6 +24,7 @@
 #include <cstddef>
 #include <vector>
 #include <utility>
+#include <ostream>
 
 namespace clang {
 namespace threadSafety {
@@ -360,8 +361,7 @@ private:
 
 
 inline std::ostream& operator<<(std::ostream& ss, const StringRef str) {
-  ss << str.data();
-  return ss;
+  return ss.write(str.data(), str.size());
 }