diff --git a/conlib/session.inc b/conlib/session.inc
index 0f09786..bbecd6a 100644
--- a/conlib/session.inc
+++ b/conlib/session.inc
@@ -323,7 +323,7 @@ class cSession {
                 while ($l) {
                     ## Structural recursion.
                     $this->serialize($var . "->" . $l, $str);
-                    eval("\$l = next(\$${var}->persistent_slots);");
+                    eval("\$l = next(\${$var}->persistent_slots);");
                 }
 
                 break;