diff --git a/unittests/ProfileData/CoverageMappingTest.cpp b/unittests/ProfileData/CoverageMappingTest.cpp
index 5477f814300..5709f91b0a4 100644
--- a/unittests/ProfileData/CoverageMappingTest.cpp
+++ b/unittests/ProfileData/CoverageMappingTest.cpp
@@ -13,6 +13,8 @@
 #include "llvm/Support/raw_ostream.h"
 #include "gtest/gtest.h"
 
+#include <string>
+
 using namespace llvm;
 using namespace coverage;