diff --git a/clang/include/clang/Basic/ConvertUTF.h b/clang/include/clang/Basic/ConvertUTF.h
index 4da2ad757223..d928f9d0f66b 100644
--- a/clang/include/clang/Basic/ConvertUTF.h
+++ b/clang/include/clang/Basic/ConvertUTF.h
@@ -87,6 +87,9 @@
 
 ------------------------------------------------------------------------ */
 
+#ifndef CLANG_BASIC_CONVERTUTF_H
+#define CLANG_BASIC_CONVERTUTF_H
+
 /* ---------------------------------------------------------------------
     The following 4 definitions are compiler-specific.
     The C standard does not guarantee that wchar_t has at least
@@ -156,4 +159,6 @@ Boolean isLegalUTF8Sequence(const UTF8 *source, const UTF8 *sourceEnd);
 }
 #endif
 
+#endif
+
 /* --------------------------------------------------------------------- */