diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 1828dc6c0408..962eb5d41a9e 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -3943,23 +3943,33 @@ bool Sema::SemaBuiltinVAStartARM(CallExpr *Call) {
   if (checkVAStartIsInVariadicFunction(*this, Func))
     return true;
 
-  const struct {
-    unsigned ArgNo;
-    QualType Type;
-  } ArgumentTypes[] = {
-    { 1, Context.getPointerType(Context.CharTy.withConst()) },
-    { 2, Context.getSizeType() },
-  };
+  // __va_start on Windows does not validate the parameter qualifiers
 
-  for (const auto &AT : ArgumentTypes) {
-    const Expr *Arg = Call->getArg(AT.ArgNo)->IgnoreParens();
-    if (Arg->getType().getCanonicalType() == AT.Type.getCanonicalType())
-      continue;
-    Diag(Arg->getLocStart(), diag::err_typecheck_convert_incompatible)
-      << Arg->getType() << AT.Type << 1 /* different class */
-      << 0 /* qualifier difference */ << 3 /* parameter mismatch */
-      << AT.ArgNo + 1 << Arg->getType() << AT.Type;
-  }
+  const Expr *Arg1 = Call->getArg(1)->IgnoreParens();
+  const Type *Arg1Ty = Arg1->getType().getCanonicalType().getTypePtr();
+
+  const Expr *Arg2 = Call->getArg(2)->IgnoreParens();
+  const Type *Arg2Ty = Arg2->getType().getCanonicalType().getTypePtr();
+
+  const QualType &ConstCharPtrTy =
+      Context.getPointerType(Context.CharTy.withConst());
+  if (!Arg1Ty->isPointerType() ||
+      Arg1Ty->getPointeeType().withoutLocalFastQualifiers() != Context.CharTy)
+    Diag(Arg1->getLocStart(), diag::err_typecheck_convert_incompatible)
+        << Arg1->getType() << ConstCharPtrTy
+        << 1 /* different class */
+        << 0 /* qualifier difference */
+        << 3 /* parameter mismatch */
+        << 2 << Arg1->getType() << ConstCharPtrTy;
+
+  const QualType SizeTy = Context.getSizeType();
+  if (Arg2Ty->getCanonicalTypeInternal().withoutLocalFastQualifiers() != SizeTy)
+    Diag(Arg2->getLocStart(), diag::err_typecheck_convert_incompatible)
+        << Arg2->getType() << SizeTy
+        << 1 /* different class */
+        << 0 /* qualifier difference */
+        << 3 /* parameter mismatch */
+        << 3 << Arg2->getType() << SizeTy;
 
   return false;
 }
diff --git a/clang/test/SemaCXX/microsoft-varargs.cpp b/clang/test/SemaCXX/microsoft-varargs.cpp
index 35f31a97c4f1..5b0f90eb5ca0 100644
--- a/clang/test/SemaCXX/microsoft-varargs.cpp
+++ b/clang/test/SemaCXX/microsoft-varargs.cpp
@@ -20,3 +20,8 @@ int builtin(int i, ...) {
   return __builtin_va_arg(ap, int);
 }
 
+void test___va_start_ignore_const(const char *format, ...) {
+  va_list args;
+  ((void)(__va_start(&args, (&const_cast<char &>(reinterpret_cast<const volatile char &>(format))), ((sizeof(format) + 4 - 1) & ~(4 - 1)), (&const_cast<char &>(reinterpret_cast<const volatile char &>(format))))));
+}
+