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
@@ -9145,6 +9145,8 @@
   "__block attribute not allowed, only allowed on local variables">;
 def err_block_on_vm : Error<
   "__block attribute not allowed on declaration with a variably modified type">;
+def err_sizeless_nonlocal : Error<
+  "non-local variable with sizeless type %0">;
 
 def err_vec_builtin_non_vector : Error<
  "first two arguments to %0 must be vectors">;
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7939,6 +7939,12 @@
     return;
   }
 
+  if (!NewVD->hasLocalStorage() && T->isSizelessType()) {
+    Diag(NewVD->getLocation(), diag::err_sizeless_nonlocal) << T;
+    NewVD->setInvalidDecl();
+    return;
+  }
+
   if (isVM && NewVD->hasAttr<BlocksAttr>()) {
     Diag(NewVD->getLocation(), diag::err_block_on_vm);
     NewVD->setInvalidDecl();
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
@@ -5,6 +5,10 @@
 typedef __SVInt8_t svint8_t;
 typedef __SVInt16_t svint16_t;
 
+svint8_t global_int8;          // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+extern svint8_t extern_int8;   // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+static svint8_t static_int8;   // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+__thread svint8_t thread_int8; // expected-error {{non-local variable with sizeless type 'svint8_t'}}
 svint8_t *global_int8_ptr;
 extern svint8_t *extern_int8_ptr;
 static svint8_t *static_int8_ptr;
@@ -48,6 +52,8 @@
 struct incomplete_struct *incomplete_ptr;
 
 void func(int sel) {
+  static svint8_t static_int8; // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+
   svint8_t local_int8;
   svint16_t local_int16;
 
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
@@ -10,6 +10,10 @@
 typedef __SVInt8_t svint8_t;
 typedef __SVInt16_t svint16_t;
 
+svint8_t global_int8;          // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+extern svint8_t extern_int8;   // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+static svint8_t static_int8;   // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+__thread svint8_t thread_int8; // expected-error {{non-local variable with sizeless type 'svint8_t'}}
 svint8_t *global_int8_ptr;
 extern svint8_t *extern_int8_ptr;
 static svint8_t *static_int8_ptr;
@@ -58,6 +62,8 @@
 struct incomplete_struct *incomplete_ptr;
 
 void func(int sel) {
+  static svint8_t static_int8; // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+
   svint8_t local_int8;
   svint16_t local_int16;