Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -2235,10 +2235,10 @@
 def warn_cconv_ignored : Warning<
   "calling convention %0 ignored for this target">, InGroup<IgnoredAttributes>;
 def err_cconv_knr : Error<
-  "function with no prototype cannot use %0 calling convention">;
+  "function with no prototype cannot use the callee-cleanup %0 calling convention">;
 def warn_cconv_knr : Warning<
-  "function with no prototype cannot use %0 calling convention">,
-  DefaultError, InGroup<DiagGroup<"missing-prototype-for-cc">>;
+  "function with no prototype cannot use the callee-cleanup %0 calling convention">,
+  InGroup<DiagGroup<"missing-prototype-for-cc">>;
 def err_cconv_varargs : Error<
   "variadic function cannot use %0 calling convention">;
 def warn_cconv_varargs : Warning<
Index: test/Sema/decl-microsoft-call-conv.c
===================================================================
--- test/Sema/decl-microsoft-call-conv.c
+++ test/Sema/decl-microsoft-call-conv.c
@@ -12,10 +12,10 @@
 void __pascal CrcGenerateTablePascal(void);
 void __pascal CrcGenerateTablePascal() {}
 
-void __fastcall CrcGenerateTableNoProtoFastcall() {} // expected-error{{function with no prototype cannot use fastcall calling convention}}
-void __stdcall CrcGenerateTableNoProtoStdcall() {} // expected-error{{function with no prototype cannot use stdcall calling convention}}
-void __thiscall CrcGenerateTableNoProtoThiscall() {} // expected-error{{function with no prototype cannot use thiscall calling convention}}
-void __pascal CrcGenerateTableNoProtoPascal() {} // expected-error{{function with no prototype cannot use pascal calling convention}}
+void __fastcall CrcGenerateTableNoProtoFastcall() {} // expected-error{{function with no prototype cannot use the callee-cleanup fastcall calling convention}}
+void __stdcall CrcGenerateTableNoProtoStdcall() {} // expected-warning{{function with no prototype cannot use the callee-cleanup stdcall calling convention}}
+void __thiscall CrcGenerateTableNoProtoThiscall() {} // expected-error{{function with no prototype cannot use the callee-cleanup thiscall calling convention}}
+void __pascal CrcGenerateTableNoProtoPascal() {} // expected-error{{function with no prototype cannot use the callee-cleanup pascal calling convention}}
 
 // Regular calling convention is fine.
 void CrcGenerateTableNoProto() {}
@@ -23,7 +23,7 @@
 
 // In system headers, the stdcall version should be a warning.
 # 1 "fake_system_header.h" 1 3 4
-void __fastcall SystemHeaderFastcall() {} // expected-error{{function with no prototype cannot use fastcall calling convention}}
+void __fastcall SystemHeaderFastcall() {} // expected-error{{function with no prototype cannot use the callee-cleanup fastcall calling convention}}
 void __stdcall SystemHeaderStdcall() {}
-void __thiscall SystemHeaderThiscall() {} // expected-error{{function with no prototype cannot use thiscall calling convention}}
-void __pascal SystemHeaderPascal() {} // expected-error{{function with no prototype cannot use pascal calling convention}}
+void __thiscall SystemHeaderThiscall() {} // expected-error{{function with no prototype cannot use the callee-cleanup thiscall calling convention}}
+void __pascal SystemHeaderPascal() {} // expected-error{{function with no prototype cannot use the callee-cleanup pascal calling convention}}