diff --git a/Source/Dafny/Compilers/Compiler-Csharp.cs b/Source/Dafny/Compilers/Compiler-Csharp.cs
index 8df020a7aa3..b60787eb9ae 100644
--- a/Source/Dafny/Compilers/Compiler-Csharp.cs
+++ b/Source/Dafny/Compilers/Compiler-Csharp.cs
@@ -1331,7 +1331,9 @@ public bool ProcessDllImport(MemberDecl decl, ConcreteSyntaxTree wr) {
     protected override ConcreteSyntaxTree EmitTailCallStructure(MemberDecl member, ConcreteSyntaxTree wr) {
       Contract.Assume((member is Method m0 && m0.IsTailRecursive) || (member is Function f0 && f0.IsTailRecursive)); // precondition
       if (!member.IsStatic && !NeedsCustomReceiver(member)) {
-        wr.WriteLine("var _this = this;");
+        var receiverType =  member.EnclosingClass is DatatypeDecl dt ?
+          "_I" + dt.CompileName + TypeParameters(SelectNonGhost(dt, dt.TypeArgs)) : "var";
+        wr.WriteLine($"{receiverType} _this = this;");
       }
       wr.Fork(-1).WriteLine("TAIL_CALL_START: ;");
       return wr;