diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index c9d400f..3a7f02c 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -619,6 +619,7 @@
            .Case("address_sanitizer", LangOpts.AddressSanitizer)
            .Case("attribute_analyzer_noreturn", true)
            .Case("attribute_availability", true)
+           .Case("attribute_availability_with_message", true)
            .Case("attribute_cf_returns_not_retained", true)
            .Case("attribute_cf_returns_retained", true)
            .Case("attribute_deprecated_with_message", true)
diff --git a/test/Sema/attr-availability.c b/test/Sema/attr-availability.c
index a13e351..b4a6f96 100644
--- a/test/Sema/attr-availability.c
+++ b/test/Sema/attr-availability.c
@@ -37,3 +37,9 @@
 void f7(int) __attribute__((availability(ios,introduced=2.0)));
 void f7(int) __attribute__((availability(ios,deprecated=3.0))); // expected-note {{previous attribute is here}}
 void f7(int) __attribute__((availability(ios,deprecated=4.0))); // expected-warning {{availability does not match previous declaration}}
+
+
+// <rdar://problem/11886458>
+#if !__has_feature(attribute_availability_with_message)
+# error "Missing __has_feature"
+#endif