1 files changed, 1 insertions, 1 deletions
diff --git a/src/cli/runtime/Var.cs b/src/cli/runtime/Var.cs
index 13d10034..cb0327e7 100644
--- a/src/cli/runtime/Var.cs
+++ b/src/cli/runtime/Var.cs
@@ -49,7 +49,7 @@ Binding getThreadBinding()
	{
         if (b == null)
             newtb = tb.without(thread);
         else
-            newtb = tb.assoc(thread, b);
+            newtb = (IPersistentMap)tb.assoc(thread, b);
 		} while (tb != Interlocked.CompareExchange(ref threadBindings, newtb, tb));
 }
 public IFn fn(){
 	return (IFn)getValue();
 }
 override public Object invoke(){
     return fn().invoke();