diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -5116,7 +5116,9 @@
                                                    CanonArgs);
 
     // Find the insert position again.
-    DependentTemplateSpecializationTypes.FindNodeOrInsertPos(ID, InsertPos);
+    [[maybe_unused]] auto *Nothing =
+        DependentTemplateSpecializationTypes.FindNodeOrInsertPos(ID, InsertPos);
+    assert(!Nothing && "canonical type broken");
   }
 
   void *Mem = Allocate((sizeof(DependentTemplateSpecializationType) +
@@ -5731,7 +5733,9 @@
         Canon = getAutoTypeInternal(QualType(), Keyword, IsDependent, IsPack,
                                     TypeConstraintConcept, CanonArgs, true);
         // Find the insert position again.
-        AutoTypes.FindNodeOrInsertPos(ID, InsertPos);
+        [[maybe_unused]] auto *Nothing =
+            AutoTypes.FindNodeOrInsertPos(ID, InsertPos);
+        assert(!Nothing && "canonical type broken");
       }
     } else {
       Canon = DeducedType.getCanonicalType();
diff --git a/clang/lib/AST/TemplateBase.cpp b/clang/lib/AST/TemplateBase.cpp
--- a/clang/lib/AST/TemplateBase.cpp
+++ b/clang/lib/AST/TemplateBase.cpp
@@ -321,26 +321,15 @@
 
   case Declaration:
     getParamTypeForDecl().Profile(ID);
-    ID.AddPointer(getAsDecl()? getAsDecl()->getCanonicalDecl() : nullptr);
+    ID.AddPointer(getAsDecl());
     break;
 
+  case TemplateExpansion:
+    ID.AddInteger(TemplateArg.NumExpansions);
+    LLVM_FALLTHROUGH;
   case Template:
-  case TemplateExpansion: {
-    TemplateName Template = getAsTemplateOrTemplatePattern();
-    if (TemplateTemplateParmDecl *TTP
-          = dyn_cast_or_null<TemplateTemplateParmDecl>(
-                                                Template.getAsTemplateDecl())) {
-      ID.AddBoolean(true);
-      ID.AddInteger(TTP->getDepth());
-      ID.AddInteger(TTP->getPosition());
-      ID.AddBoolean(TTP->isParameterPack());
-    } else {
-      ID.AddBoolean(false);
-      ID.AddPointer(Context.getCanonicalTemplateName(Template)
-                                                          .getAsVoidPointer());
-    }
+    getAsTemplateOrTemplatePattern().Profile(ID);
     break;
-  }
 
   case Integral:
     getAsIntegral().Profile(ID);
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -5643,7 +5643,8 @@
     if (CheckTemplateTemplateArgument(TempParm, Params, Arg))
       return true;
 
-    Converted.push_back(Arg.getArgument());
+    Converted.push_back(
+        Context.getCanonicalTemplateArgument(Arg.getArgument()));
     break;
 
   case TemplateArgument::Expression:
@@ -5813,13 +5814,14 @@
         if (!ArgumentPack.empty()) {
           // If we were part way through filling in an expanded parameter pack,
           // fall back to just producing individual arguments.
-          Converted.insert(Converted.end(),
-                           ArgumentPack.begin(), ArgumentPack.end());
+          for (const TemplateArgument &I : ArgumentPack)
+            Converted.push_back(Context.getCanonicalTemplateArgument(I));
           ArgumentPack.clear();
         }
 
         while (ArgIdx < NumArgs) {
-          Converted.push_back(NewArgs[ArgIdx].getArgument());
+          Converted.push_back(Context.getCanonicalTemplateArgument(
+              NewArgs[ArgIdx].getArgument()));
           ++ArgIdx;
         }
 
@@ -5952,7 +5954,8 @@
   if (ArgIdx < NumArgs && CurrentInstantiationScope &&
       CurrentInstantiationScope->getPartiallySubstitutedPack()) {
     while (ArgIdx < NumArgs && NewArgs[ArgIdx].getArgument().isPackExpansion())
-      Converted.push_back(NewArgs[ArgIdx++].getArgument());
+      Converted.push_back(Context.getCanonicalTemplateArgument(
+          NewArgs[ArgIdx++].getArgument()));
   }
 
   // If we have any leftover arguments, then there were too many arguments.
diff --git a/clang/test/SemaTemplate/concepts.cpp b/clang/test/SemaTemplate/concepts.cpp
--- a/clang/test/SemaTemplate/concepts.cpp
+++ b/clang/test/SemaTemplate/concepts.cpp
@@ -256,3 +256,9 @@
 C auto **&j2 = g();  // expected-error {{deduced type 'int' does not satisfy 'C'}}
 C auto **&&j3 = g(); // expected-error {{deduced type 'int' does not satisfy 'C'}}
 }
+
+namespace GH55567 {
+template<class, template <class> class> concept C = true;
+template <class> struct S {};
+void f(C<GH55567::S> auto);
+} // namespace GH55567