diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 794ef23f07619a..91112860a2d029 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -793,6 +793,7 @@ def ext_main_used : Extension<
 /// parser diagnostics
 def ext_no_declarators : ExtWarn<"declaration does not declare anything">,
   InGroup<MissingDeclarations>;
+def err_no_declarators : Error<"declaration does not declare anything">;
 def ext_typedef_without_a_name : ExtWarn<"typedef requires a name">,
   InGroup<MissingDeclarations>;
 def err_typedef_not_identifier : Error<"typedef name must be an identifier">;
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index ddbf086ea63851..9b9d164dcbc1b8 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4766,7 +4766,10 @@ Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS, DeclSpec &DS,
   if (!DeclaresAnything) {
     // In C, we allow this as a (popular) extension / bug. Don't bother
     // producing further diagnostics for redundant qualifiers after this.
-    Diag(DS.getBeginLoc(), diag::ext_no_declarators) << DS.getSourceRange();
+    Diag(DS.getBeginLoc(), (IsExplicitInstantiation || !TemplateParams.empty())
+                               ? diag::err_no_declarators
+                               : diag::ext_no_declarators)
+        << DS.getSourceRange();
     return TagD;
   }
 
diff --git a/clang/test/Parser/cxx-template-decl.cpp b/clang/test/Parser/cxx-template-decl.cpp
index 64e7ca921f575b..7455b1d0ffe72c 100644
--- a/clang/test/Parser/cxx-template-decl.cpp
+++ b/clang/test/Parser/cxx-template-decl.cpp
@@ -12,7 +12,7 @@ export template x;      // expected-error {{expected '<' after 'template'}}
 export template<class T> class x0; // expected-warning {{exported templates are unsupported}}
 template < ;            // expected-error {{expected template parameter}} \
 // expected-error{{expected ',' or '>' in template-parameter-list}} \
-// expected-warning {{declaration does not declare anything}}
+// expected-error {{declaration does not declare anything}}
 template <int +> struct x1; // expected-error {{expected ',' or '>' in template-parameter-list}}
 
 // verifies that we only walk to the ',' & still produce errors on the rest of the template parameters
@@ -286,3 +286,12 @@ namespace PR45239 {
   template<int> int b;
   template<int> auto f() -> b<0>; // expected-error +{{}}
 }
+
+namespace PR46231 {
+  template; // expected-error {{declaration does not declare anything}}
+  template<>; // expected-error {{declaration does not declare anything}}
+  template<int>; // expected-error {{declaration does not declare anything}}
+  template int; // expected-error {{declaration does not declare anything}}
+  template<> int; // expected-error {{declaration does not declare anything}}
+  template<int> int; // expected-error {{declaration does not declare anything}}
+}
diff --git a/clang/test/SemaCXX/PR16677.cpp b/clang/test/SemaCXX/PR16677.cpp
index efa4faaacd6932..3ad76c6d861d7d 100644
--- a/clang/test/SemaCXX/PR16677.cpp
+++ b/clang/test/SemaCXX/PR16677.cpp
@@ -11,5 +11,5 @@ template<class T,  // Should be angle bracket instead of comma
 class Derived : public Base<T> { // expected-error{{'Derived' cannot be defined in a type specifier}}
   Class_With_Destructor member;
 }; // expected-error{{expected ',' or '>' in template-parameter-list}}
-   // expected-warning@-1{{declaration does not declare anything}}
+   // expected-error@-1{{declaration does not declare anything}}
 
diff --git a/clang/test/SemaCXX/invalid-template-params.cpp b/clang/test/SemaCXX/invalid-template-params.cpp
index 0c463fe13d5b0c..21220f3fea3451 100644
--- a/clang/test/SemaCXX/invalid-template-params.cpp
+++ b/clang/test/SemaCXX/invalid-template-params.cpp
@@ -5,7 +5,7 @@ template<class> class Foo {
                       // expected-note@-1 {{'UBar' declared here}}
   void foo1(); // expected-error {{a non-type template parameter cannot have type 'class UBar'}}
                // expected-error@-1 {{expected ',' or '>' in template-parameter-list}}
-               // expected-warning@-2 {{declaration does not declare anything}}
+               // expected-error@-2 {{declaration does not declare anything}}
 };
 
 Foo<int>::UBar g1; // expected-error {{no type named 'UBar' in 'Foo<int>'}}
@@ -16,7 +16,7 @@ class C0 {
   struct S0 {}; // expected-error {{'S0' cannot be defined in a type specifier}}
                 // expected-error@-1 {{cannot combine with previous 'type-name' declaration specifier}}
                 // expected-error@-2 {{expected ',' or '>' in template-parameter-list}}
-                // expected-warning@-3 {{declaration does not declare anything}}
+                // expected-error@-3 {{declaration does not declare anything}}
   C0() : m(new S0<int>) {} // expected-error {{expected '(' for function-style cast or type construction}}
                            // expected-error@-1 {{expected expression}}
   S0<int> *m; // expected-error {{expected member name or ';' after declaration specifiers}}
diff --git a/clang/test/SemaTemplate/template-decl-fail.cpp b/clang/test/SemaTemplate/template-decl-fail.cpp
index ad134cdf225c2a..7019caa2c2f318 100644
--- a/clang/test/SemaTemplate/template-decl-fail.cpp
+++ b/clang/test/SemaTemplate/template-decl-fail.cpp
@@ -4,7 +4,7 @@ template<typename T> typedef T X; // expected-error{{typedef cannot be a templat
 
 template<typename T>
 enum t0 { A = T::x }; // expected-error{{enumeration cannot be a template}} \
-                      // expected-warning{{declaration does not declare anything}}
+                      // expected-error{{declaration does not declare anything}}
 
 enum e0 {};
 template<int x> enum e0 f0(int a=x) {}