diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1695,9 +1695,6 @@
 def ext_missing_exception_specification : ExtWarn<
   err_missing_exception_specification.Text>,
   InGroup<DiagGroup<"missing-exception-spec">>;
-def ext_ms_missing_exception_specification : ExtWarn<
-  err_missing_exception_specification.Text>,
-  InGroup<MicrosoftExceptionSpec>;
 def err_noexcept_needs_constant_expression : Error<
   "argument to noexcept specifier must be a constant expression">;
 def err_exception_spec_not_parsed : Error<
diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -391,10 +391,11 @@
         NewProto->getExtProtoInfo().withExceptionSpec(ESI)));
   }
 
-  if (getLangOpts().MSVCCompat && ESI.Type != EST_DependentNoexcept) {
-    // Allow missing exception specifications in redeclarations as an extension.
-    DiagID = diag::ext_ms_missing_exception_specification;
-    ReturnValueOnError = false;
+  if (getLangOpts().MSVCCompat &&
+      !(ESI.Type == EST_DependentNoexcept || ESI.Type == EST_BasicNoexcept)) {
+    // Allow missing exception specifications in redeclarations as an extension
+    // without a warning.
+    return false;
   } else if (New->isReplaceableGlobalAllocationFunction() &&
              ESI.Type != EST_DependentNoexcept) {
     // Allow missing exception specifications in redeclarations as an extension,
diff --git a/clang/test/SemaCXX/MicrosoftCompatibility.cpp b/clang/test/SemaCXX/MicrosoftCompatibility.cpp
--- a/clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ b/clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -377,14 +377,14 @@
 #endif
 };
 
-}
+void f4() throw();
+void f4() {}
 
-namespace PR25265 {
-struct S {
-  int fn() throw(); // expected-note {{previous declaration is here}}
-};
+__declspec(nothrow) void f5();
+void f5() {}
 
-int S::fn() { return 0; } // expected-warning {{is missing exception specification}}
+void f6() noexcept; // expected-note {{previous declaration is here}}
+void f6() {}        // expected-error {{'f6' is missing exception specification 'noexcept'}}
 }
 
 namespace PR43265 {