diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 7ebf06a04fa7..780d48958cb9 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -1119,7 +1119,7 @@ void Parser::ParseAvailabilityAttribute(IdentifierInfo &Availability,
       // Also reject wide string literals.
       if (StringLiteral *MessageStringLiteral =
               cast_or_null<StringLiteral>(MessageExpr.get())) {
-        if (MessageStringLiteral->getCharByteWidth() != 1) {
+        if (!MessageStringLiteral->isAscii()) {
           Diag(MessageStringLiteral->getSourceRange().getBegin(),
                diag::err_expected_string_literal)
             << /*Source='availability attribute'*/ 2;
diff --git a/clang/test/Parser/attr-availability.c b/clang/test/Parser/attr-availability.c
index d812296d9354..d3b640a2feea 100644
--- a/clang/test/Parser/attr-availability.c
+++ b/clang/test/Parser/attr-availability.c
@@ -22,6 +22,14 @@ void f7() __attribute__((availability(macosx,message=L"wide"))); // expected-err
 
 void f8() __attribute__((availability(macosx,message="a" L"b"))); // expected-error {{expected string literal for optional message in 'availability' attribute}}
 
+void f9() __attribute__((availability(macosx,message=u8"b"))); // expected-error {{expected string literal for optional message in 'availability' attribute}}
+
+void f10() __attribute__((availability(macosx,message="a" u8"b"))); // expected-error {{expected string literal for optional message in 'availability' attribute}}
+
+void f11() __attribute__((availability(macosx,message=u"b"))); // expected-error {{expected string literal for optional message in 'availability' attribute}}
+
+void f12() __attribute__((availability(macosx,message="a" u"b"))); // expected-error {{expected string literal for optional message in 'availability' attribute}}
+
 // rdar://10095131
 enum E{
     gorf __attribute__((availability(macosx,introduced=8.5, message = 10.0))), // expected-error {{expected string literal for optional message in 'availability' attribute}}