diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index e331df86235b23..6bc202ecd5b021 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -12982,8 +12982,10 @@ static QualType getCommonSugarTypeNode(ASTContext &Ctx, const Type *X,
     SmallVector<TemplateArgument, 8> As;
     if (CD &&
         getCommonTemplateArguments(Ctx, As, AX->getTypeConstraintArguments(),
-                                   AY->getTypeConstraintArguments()))
+                                   AY->getTypeConstraintArguments())) {
       CD = nullptr; // The arguments differ, so make it unconstrained.
+      As.clear();
+    }
 
     // Both auto types can't be dependent, otherwise they wouldn't have been
     // sugar. This implies they can't contain unexpanded packs either.
diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index e1686a7c69d522..c0d225034be892 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -4630,6 +4630,7 @@ AutoType::AutoType(QualType DeducedAsType, AutoTypeKeyword Keyword,
   AutoTypeBits.Keyword = (unsigned)Keyword;
   AutoTypeBits.NumArgs = TypeConstraintArgs.size();
   this->TypeConstraintConcept = TypeConstraintConcept;
+  assert(TypeConstraintConcept || AutoTypeBits.NumArgs == 0);
   if (TypeConstraintConcept) {
     auto *ArgBuffer =
         const_cast<TemplateArgument *>(getTypeConstraintArguments().data());