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
@@ -1537,6 +1537,9 @@
 def err_incomplete_in_exception_spec : Error<
   "%select{|pointer to |reference to }0incomplete type %1 is not allowed "
   "in exception specification">;
+def err_sizeless_in_exception_spec : Error<
+  "%select{|reference to }0sizeless type %1 is not allowed "
+  "in exception specification">;
 def ext_incomplete_in_exception_spec : ExtWarn<err_incomplete_in_exception_spec.Text>,
   InGroup<MicrosoftExceptionSpec>;
 def err_rref_in_exception_spec : 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
@@ -167,6 +167,14 @@
       RequireCompleteType(Range.getBegin(), PointeeT, DiagID, Kind, Range))
     return ReturnValueOnError;
 
+  // The MSVC compatibility mode doesn't extend to sizeless types,
+  // so diagnose them separately.
+  if (PointeeT->isSizelessType() && Kind != 1) {
+    Diag(Range.getBegin(), diag::err_sizeless_in_exception_spec)
+        << (Kind == 2 ? 1 : 0) << PointeeT << Range;
+    return true;
+  }
+
   return false;
 }
 
diff --git a/clang/test/SemaCXX/sizeless-1.cpp b/clang/test/SemaCXX/sizeless-1.cpp
--- a/clang/test/SemaCXX/sizeless-1.cpp
+++ b/clang/test/SemaCXX/sizeless-1.cpp
@@ -345,6 +345,12 @@
 constexpr int ce_taking_int8(svint8_t) { return 1; } // expected-error {{constexpr function's 1st parameter type 'svint8_t' (aka '__SVInt8_t') is not a literal type}}
 #endif
 
+#if __cplusplus < 201703L
+void throwing_func() throw(svint8_t); // expected-error {{sizeless type 'svint8_t' (aka '__SVInt8_t') is not allowed in exception specification}}
+void throwing_pointer_func() throw(svint8_t *);
+void throwing_reference_func() throw(svint8_t &); // expected-error {{reference to sizeless type 'svint8_t' (aka '__SVInt8_t') is not allowed in exception specification}}
+#endif
+
 template <typename T>
 void template_fn_direct(T) {}
 template <typename T>