diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index b971a04..1515a35 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1638,9 +1638,8 @@
 }
 
 ParmVarDecl *TemplateDeclInstantiator::VisitParmVarDecl(ParmVarDecl *D) {
-  return SemaRef.SubstParmVarDecl(D, TemplateArgs, /*indexAdjustment*/ 0,
-                                  Optional<unsigned>(),
-                                  /*ExpectParameterPack=*/false);
+  return SemaRef.SubstParmVarDecl(D, TemplateArgs, /*indexAdjustment*/ 0, None,
+                                  /*ExpectParameterPack=*/ false);
 }
 
 Decl *TemplateDeclInstantiator::VisitTemplateTypeParmDecl(