diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 51e5973098c14..0eadc1c773597 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -241,7 +241,8 @@ Improvements to Clang's diagnostics
 - Fixed fix-it hint for fold expressions. Clang now correctly places the suggested right
   parenthesis when diagnosing malformed fold expressions. (#GH151787)
 - Added fix-it hint for when scoped enumerations require explicit conversions for binary operations. (#GH24265)
-
+- Constant template parameters are now type checked in template definitions,
+  including template template parameters.
 - Fixed an issue where emitted format-signedness diagnostics were not associated with an appropriate
   diagnostic id. Besides being incorrect from an API standpoint, this was user visible, e.g.:
   "format specifies type 'unsigned int' but the argument has type 'int' [-Wformat]"
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index d6b25c2d83613..faeba6ada0c6b 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -5482,9 +5482,7 @@ bool Sema::CheckTemplateArgument(NamedDecl *Param, TemplateArgumentLoc &ArgLoc,
     if (NTTP->isParameterPack() && NTTP->isExpandedParameterPack())
       NTTPType = NTTP->getExpansionType(ArgumentPackIndex);
 
-    if (NTTPType->isInstantiationDependentType() &&
-        !isa<TemplateTemplateParmDecl>(Template) &&
-        !Template->getDeclContext()->isDependentContext()) {
+    if (NTTPType->isInstantiationDependentType()) {
       // Do substitution on the type of the non-type template parameter.
       InstantiatingTemplate Inst(*this, TemplateLoc, Template, NTTP,
                                  CTAI.SugaredConverted,
@@ -5494,6 +5492,7 @@ bool Sema::CheckTemplateArgument(NamedDecl *Param, TemplateArgumentLoc &ArgLoc,
 
       MultiLevelTemplateArgumentList MLTAL(Template, CTAI.SugaredConverted,
                                            /*Final=*/true);
+      MLTAL.addOuterRetainedLevels(NTTP->getDepth());
       // If the parameter is a pack expansion, expand this slice of the pack.
       if (auto *PET = NTTPType->getAs<PackExpansionType>()) {
         Sema::ArgPackSubstIndexRAII SubstIndex(*this, ArgumentPackIndex);
diff --git a/clang/test/SemaTemplate/temp_arg_template.cpp b/clang/test/SemaTemplate/temp_arg_template.cpp
index aa53dba652050..431e19741ece9 100644
--- a/clang/test/SemaTemplate/temp_arg_template.cpp
+++ b/clang/test/SemaTemplate/temp_arg_template.cpp
@@ -117,16 +117,8 @@ namespace CheckDependentNonTypeParamTypes {
       X<int, long, 3> x;
     }
     void h() {
-      // FIXME: If we accept A<B> at all, it's not obvious what should happen
-      // here. While parsing the template, we form
-      //   X<unsigned char, int, (unsigned char)1234>
-      // but in the final instantiation do we get
-      //   B<unsigned char, int, (int)1234>
-      // or
-      //   B<unsigned char, int, (int)(unsigned char)1234>
-      // ?
       X<unsigned char, int, 1234> x;
-      int check[x.value == 1234 ? 1 : -1];
+      // expected-error@-1 {{evaluates to 1234, which cannot be narrowed to type 'unsigned char'}}
     }
   };
 
@@ -143,6 +135,20 @@ namespace CheckDependentNonTypeParamTypes {
     ab.g();
     ab.h();
   }
+
+  template<class> struct C {
+    template<class T, T V> struct D {};
+    using T = D<char, 1234>;
+    // expected-error@-1 {{evaluates to 1234, which cannot be narrowed to type 'char'}}
+  };
+
+  template<class T> struct E {
+    template <template <T V> class TT> struct F {
+      using X = TT<1234>;
+    };
+  };
+  // FIXME: This should be rejected, as there are no valid instantiations for E<char>::F
+  template struct E<char>;
 }
 
 namespace PR32185 {