diff --git a/unittests/ADT/APIntTest.cpp b/unittests/ADT/APIntTest.cpp
index 098140c50c6..0113ddde532 100644
--- a/unittests/ADT/APIntTest.cpp
+++ b/unittests/ADT/APIntTest.cpp
@@ -10,6 +10,7 @@
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/SmallString.h"
 #include "gtest/gtest.h"
+#include <array>
 #include <ostream>
 
 using namespace llvm;