diff --git a/clang/lib/Headers/inttypes.h b/clang/lib/Headers/inttypes.h
--- a/clang/lib/Headers/inttypes.h
+++ b/clang/lib/Headers/inttypes.h
@@ -21,7 +21,11 @@
 \*===----------------------------------------------------------------------===*/
 
 #ifndef __CLANG_INTTYPES_H
+// AIX system headers need stdint.h to be re-enterable if _STD_TYPES_T
+// is defined.
+#if !defined(_AIX) || !defined(_STD_TYPES_T)
 #define __CLANG_INTTYPES_H
+#endif
 
 #if defined(_MSC_VER) && _MSC_VER < 1800
 #error MSVC does not have inttypes.h prior to Visual Studio 2013
diff --git a/clang/lib/Headers/stdint.h b/clang/lib/Headers/stdint.h
--- a/clang/lib/Headers/stdint.h
+++ b/clang/lib/Headers/stdint.h
@@ -23,7 +23,11 @@
 \*===----------------------------------------------------------------------===*/
 
 #ifndef __CLANG_STDINT_H
+// AIX system headers need stdint.h to be re-enterable if _STD_TYPES_T
+// is defined.
+#if !defined(_AIX) || !defined(_STD_TYPES_T) || !defined(__STDC_HOSTED__)
 #define __CLANG_STDINT_H
+#endif
 
 /* If we're hosted, fall back to the system's stdint.h, which might have
  * additional definitions.
diff --git a/libcxx/include/inttypes.h b/libcxx/include/inttypes.h
--- a/libcxx/include/inttypes.h
+++ b/libcxx/include/inttypes.h
@@ -8,7 +8,11 @@
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP_INTTYPES_H
+// AIX system headers need inttypes.h to be re-enterable if _STD_TYPES_T
+// is defined.
+#if !defined(_AIX) || !defined(_STD_TYPES_T)
 #define _LIBCPP_INTTYPES_H
+#endif // _STD_TYPES_T
 
 /*
     inttypes.h synopsis
diff --git a/libcxx/include/stdint.h b/libcxx/include/stdint.h
--- a/libcxx/include/stdint.h
+++ b/libcxx/include/stdint.h
@@ -8,7 +8,11 @@
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP_STDINT_H
+// AIX system headers need stdint.h to be re-enterable if _STD_TYPES_T
+// is defined.
+#if !defined(_AIX) || !defined(_STD_TYPES_T)
 #define _LIBCPP_STDINT_H
+#endif // _STD_TYPES_T
 
 /*
     stdint.h synopsis