Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -2564,7 +2564,7 @@
 def note_previous_attribute : Note<"previous attribute is here">;
 def note_attribute : Note<"attribute is here">;
 def err_mismatched_ms_inheritance : Error<
-  "inheritance model does not match %select{definition|previous declaration}0">;
+  "inheritance model does not match %select{definition|previous declaration}0 (%select{single|multiple|virtual|most general}1 vs %select{single|multiple|virtual|most general}2)">;
 def warn_ignored_ms_inheritance : Warning<
   "inheritance model ignored on %select{primary template|partial specialization}0">,
   InGroup<IgnoredAttributes>;
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -2863,16 +2863,19 @@
   if (SemanticSpelling == MSInheritanceAttr::Keyword_unspecified_inheritance)
     return false;
 
+  MSInheritanceAttr::Spelling CalculatedInheritanceModel =
+      RD->calculateInheritanceModel();
   if (BestCase) {
-    if (RD->calculateInheritanceModel() == SemanticSpelling)
+    if (CalculatedInheritanceModel == SemanticSpelling)
       return false;
   } else {
-    if (RD->calculateInheritanceModel() <= SemanticSpelling)
+    if (CalculatedInheritanceModel <= SemanticSpelling)
       return false;
   }
 
   Diag(Range.getBegin(), diag::err_mismatched_ms_inheritance)
-      << 0 /*definition*/;
+      << 0 /*definition*/ << SemanticSpelling << CalculatedInheritanceModel;
+
   Diag(RD->getDefinition()->getLocation(), diag::note_defined_here)
       << RD->getNameAsString();
   return true;
@@ -3892,7 +3895,8 @@
     if (IA->getSemanticSpelling() == SemanticSpelling)
       return nullptr;
     Diag(IA->getLocation(), diag::err_mismatched_ms_inheritance)
-        << 1 /*previous declaration*/;
+        << 1 /*previous declaration*/ << SemanticSpelling
+        << IA->getSemanticSpelling();
     Diag(Range.getBegin(), diag::note_previous_ms_inheritance);
     D->dropAttr<MSInheritanceAttr>();
   }
Index: test/SemaCXX/member-pointer-ms.cpp
===================================================================
--- test/SemaCXX/member-pointer-ms.cpp
+++ test/SemaCXX/member-pointer-ms.cpp
@@ -248,6 +248,18 @@
 struct __virtual_inheritance D;
 struct D : virtual B {};
 }
+
+#ifdef VMB
+namespace WarnTest {
+struct A {};
+struct B : A { // expected-error {{inheritance model does not match definition (single vs multiple)}}
+  // expected-note@-1 {{B defined here}}
+  int B::*x;
+  virtual void f();
+};
+}
+#endif
+
 #ifdef VMB
 
 namespace PR20017 {