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
@@ -7113,10 +7113,9 @@
     : Error<"vector operands to the vector conditional must be the same type "
             "%diff{($ and $)|}0,1}">;
 
-def err_throw_incomplete : Error<
-  "cannot throw object of incomplete type %0">;
-def err_throw_incomplete_ptr : Error<
-  "cannot throw pointer to object of incomplete type %0">;
+def err_throw_incomplete_or_sizeless : Error<
+  "cannot throw %select{|pointer to }0object of %select{incomplete|sizeless}1 "
+  "type %2">;
 def warn_throw_underaligned_obj : Warning<
   "underaligned exception object thrown">,
   InGroup<UnderalignedExceptionObject>;
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -950,10 +950,9 @@
     isPointer = true;
   }
   if (!isPointer || !Ty->isVoidType()) {
-    if (RequireCompleteType(ThrowLoc, Ty,
-                            isPointer ? diag::err_throw_incomplete_ptr
-                                      : diag::err_throw_incomplete,
-                            E->getSourceRange()))
+    if (RequireCompleteSizedType(ThrowLoc, Ty,
+                                 diag::err_throw_incomplete_or_sizeless,
+                                 isPointer, E->getSourceRange()))
       return true;
 
     if (RequireNonAbstractType(ThrowLoc, ExceptionObjectTy,
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
@@ -395,6 +395,10 @@
   local_int16 = static_cast<svint16_t>(local_int8); // expected-error {{static_cast from 'svint8_t' (aka '__SVInt8_t') to 'svint16_t' (aka '__SVInt16_t') is not allowed}}
   sel = static_cast<int>(local_int8);               // expected-error {{static_cast from 'svint8_t' (aka '__SVInt8_t') to 'int' is not allowed}}
 
+  throw 1;
+  throw local_int8;      // expected-error {{cannot throw object of sizeless type 'svint8_t'}}
+  throw global_int8_ptr; // expected-error {{cannot throw pointer to object of sizeless type 'svint8_t'}}
+
   local_int8.~__SVInt8_t(); // expected-error {{object expression of non-scalar type 'svint8_t' (aka '__SVInt8_t') cannot be used in a pseudo-destructor expression}}
 
   (void)svint8_t();