diff --git a/llvm/unittests/MC/StringTableBuilderTest.cpp b/llvm/unittests/MC/StringTableBuilderTest.cpp
index 517ada5..f68350d 100644
--- a/llvm/unittests/MC/StringTableBuilderTest.cpp
+++ b/llvm/unittests/MC/StringTableBuilderTest.cpp
@@ -7,6 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/SmallString.h"
 #include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Support/Endian.h"
 #include "gtest/gtest.h"