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
@@ -6897,8 +6897,8 @@
   "array size must be specified in new expression with no initializer">;
 def err_bad_new_type : Error<
   "cannot allocate %select{function|reference}1 type %0 with new">;
-def err_new_incomplete_type : Error<
-  "allocation of incomplete type %0">;
+def err_new_incomplete_or_sizeless_type : Error<
+  "allocation of %select{incomplete|sizeless}0 type %1">;
 def err_new_array_nonconst : Error<
   "only the first dimension of an allocated array may have dynamic size">;
 def err_new_array_size_unknown_from_init : Error<
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
@@ -2340,7 +2340,8 @@
     return Diag(Loc, diag::err_bad_new_type)
       << AllocType << 1 << R;
   else if (!AllocType->isDependentType() &&
-           RequireCompleteType(Loc, AllocType, diag::err_new_incomplete_type,R))
+           RequireCompleteSizedType(
+               Loc, AllocType, diag::err_new_incomplete_or_sizeless_type, R))
     return true;
   else if (RequireNonAbstractType(Loc, AllocType,
                                   diag::err_allocation_of_abstract_type))
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
@@ -411,6 +411,15 @@
   } catch (svint8_t &) { // expected-error {{cannot catch reference to sizeless type 'svint8_t'}}
   }
 
+  new svint8_t;     // expected-error {{allocation of sizeless type 'svint8_t'}}
+  new svint8_t();   // expected-error {{allocation of sizeless type 'svint8_t'}}
+  new svint8_t[10]; // expected-error {{allocation of sizeless type 'svint8_t'}}
+  new svint8_t *;
+
+  new (global_int8_ptr) svint8_t;     // expected-error {{allocation of sizeless type 'svint8_t'}}
+  new (global_int8_ptr) svint8_t();   // expected-error {{allocation of sizeless type 'svint8_t'}}
+  new (global_int8_ptr) svint8_t[10]; // expected-error {{allocation 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();