diff --git a/clang/lib/Basic/Targets/OSTargets.h b/clang/lib/Basic/Targets/OSTargets.h
--- a/clang/lib/Basic/Targets/OSTargets.h
+++ b/clang/lib/Basic/Targets/OSTargets.h
@@ -676,6 +676,7 @@
 
     Builder.defineMacro("_AIX");
     Builder.defineMacro("__TOS_AIX__");
+    Builder.defineMacro("__HOS_AIX__");
 
     if (Opts.C11) {
       Builder.defineMacro("__STDC_NO_ATOMICS__");
diff --git a/clang/test/Preprocessor/init-ppc.c b/clang/test/Preprocessor/init-ppc.c
--- a/clang/test/Preprocessor/init-ppc.c
+++ b/clang/test/Preprocessor/init-ppc.c
@@ -431,6 +431,7 @@
 // PPC-AIX:#define __FLT_MIN_EXP__ (-125)
 // PPC-AIX:#define __FLT_MIN__ 1.17549435e-38F
 // PPC-AIX:#define __FLT_RADIX__ 2
+// PPC-AIX:#define __HOS_AIX__ 1
 // PPC-AIX:#define __INT16_C_SUFFIX__
 // PPC-AIX:#define __INT16_FMTd__ "hd"
 // PPC-AIX:#define __INT16_FMTi__ "hi"