diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 6b8a9d9..b2a8c11 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -1637,10 +1637,26 @@
 }
 
 void ASTDeclWriter::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
+  Record.push_back(D->hasTypeConstraint());
   VisitTypeDecl(D);
 
   Record.push_back(D->wasDeclaredWithTypename());
-  // TODO: Concepts - constrained parameters.
+
+  const TypeConstraint *TC = D->getTypeConstraint();
+  Record.push_back(TC != nullptr);
+  if (TC) {
+    Record.AddNestedNameSpecifierLoc(TC->getNestedNameSpecifierLoc());
+    Record.AddDeclarationNameInfo(TC->getConceptNameInfo());
+    Record.AddDeclRef(TC->getNamedConcept());
+    Record.push_back(TC->getTemplateArgsAsWritten() != nullptr);
+    if (TC->getTemplateArgsAsWritten())
+      Record.AddASTTemplateArgumentListInfo(TC->getTemplateArgsAsWritten());
+    Record.AddStmt(TC->getImmediatelyDeclaredConstraint());
+    Record.push_back(D->isExpandedParameterPack());
+    if (D->isExpandedParameterPack())
+      Record.push_back(D->getNumExpansionParameters());
+  }
+
   bool OwnsDefaultArg = D->hasDefaultArgument() &&
                         !D->defaultArgumentWasInherited();
   Record.push_back(OwnsDefaultArg);
@@ -1670,7 +1686,6 @@
 
     Code = serialization::DECL_EXPANDED_NON_TYPE_TEMPLATE_PARM_PACK;
   } else {
-    // TODO: Concepts - constrained parameters.
     // Rest of NonTypeTemplateParmDecl.
     Record.push_back(D->isParameterPack());
     bool OwnsDefaultArg = D->hasDefaultArgument() &&
@@ -1700,7 +1715,6 @@
       Record.AddTemplateParameterList(D->getExpansionTemplateParameters(I));
     Code = serialization::DECL_EXPANDED_TEMPLATE_TEMPLATE_PARM_PACK;
   } else {
-    // TODO: Concepts - constrained parameters.
     // Rest of TemplateTemplateParmDecl.
     Record.push_back(D->isParameterPack());
     bool OwnsDefaultArg = D->hasDefaultArgument() &&