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
@@ -6234,8 +6234,8 @@
   "cannot %select{decrement|increment}1 value of type %0">;
 def err_typecheck_expect_int : Error<
   "used type %0 where integer is required">;
-def err_typecheck_arithmetic_incomplete_type : Error<
-  "arithmetic on a pointer to an incomplete type %0">;
+def err_typecheck_arithmetic_incomplete_or_sizeless_type : Error<
+  "arithmetic on a pointer to %select{an incomplete|sizeless}0 type %1">;
 def err_typecheck_pointer_arith_function_type : Error<
   "arithmetic on%select{ a|}0 pointer%select{|s}0 to%select{ the|}2 "
   "function type%select{|s}2 %1%select{| and %3}2">;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -9534,9 +9534,10 @@
 
   assert(ResType->isAnyPointerType() && !ResType->isDependentType());
   QualType PointeeTy = ResType->getPointeeType();
-  return S.RequireCompleteType(Loc, PointeeTy,
-                               diag::err_typecheck_arithmetic_incomplete_type,
-                               PointeeTy, Operand->getSourceRange());
+  return S.RequireCompleteSizedType(
+      Loc, PointeeTy,
+      diag::err_typecheck_arithmetic_incomplete_or_sizeless_type,
+      Operand->getSourceRange());
 }
 
 /// Check the validity of an arithmetic pointer operand.
diff --git a/clang/test/Sema/sizeless-1.c b/clang/test/Sema/sizeless-1.c
--- a/clang/test/Sema/sizeless-1.c
+++ b/clang/test/Sema/sizeless-1.c
@@ -137,6 +137,8 @@
   dump(&volatile_int8);
   dump(&const_volatile_int8);
 
+  dump(&local_int8 + 1); // expected-error {{arithmetic on a pointer to sizeless type}}
+
   *&local_int8 = local_int8;
   *&const_int8 = local_int8; // expected-error {{read-only variable is not assignable}}
   *&volatile_int8 = local_int8;
@@ -158,6 +160,16 @@
   noproto(local_int8);
   varargs(1, local_int8, local_int16);
 
+  global_int8_ptr++;                 // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr--;                 // expected-error {{arithmetic on a pointer to sizeless type}}
+  ++global_int8_ptr;                 // expected-error {{arithmetic on a pointer to sizeless type}}
+  --global_int8_ptr;                 // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr + 1;               // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr - 1;               // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr += 1;              // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr -= 1;              // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr - global_int8_ptr; // expected-error {{arithmetic on a pointer to sizeless type}}
+
   +init_int8;       // expected-error {{invalid argument type 'svint8_t'}}
   ++init_int8;      // expected-error {{cannot increment value of type 'svint8_t'}}
   init_int8++;      // expected-error {{cannot increment value of type 'svint8_t'}}
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
@@ -158,6 +158,8 @@
   dump(&volatile_int8);
   dump(&const_volatile_int8);
 
+  dump(&local_int8 + 1); // expected-error {{arithmetic on a pointer to sizeless type}}
+
   *&local_int8 = local_int8;
   *&const_int8 = local_int8; // expected-error {{read-only variable is not assignable}}
   *&volatile_int8 = local_int8;
@@ -178,6 +180,16 @@
 
   varargs(1, local_int8, local_int16);
 
+  global_int8_ptr++;                 // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr--;                 // expected-error {{arithmetic on a pointer to sizeless type}}
+  ++global_int8_ptr;                 // expected-error {{arithmetic on a pointer to sizeless type}}
+  --global_int8_ptr;                 // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr + 1;               // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr - 1;               // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr += 1;              // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr -= 1;              // expected-error {{arithmetic on a pointer to sizeless type}}
+  global_int8_ptr - global_int8_ptr; // expected-error {{arithmetic on a pointer to sizeless type}}
+
   +init_int8;       // expected-error {{invalid argument type 'svint8_t'}}
   ++init_int8;      // expected-error {{cannot increment value of type 'svint8_t'}}
   init_int8++;      // expected-error {{cannot increment value of type 'svint8_t'}}