diff --git a/lib/sandbox.js b/lib/sandbox.js
index 14fb63e..130bfcd 100644
--- a/lib/sandbox.js
+++ b/lib/sandbox.js
@@ -54,7 +54,7 @@ class SandboxDate {
 
 function random() {
   if (!state.rng)
-    state.rng = seedrandom(sessionContext.timestamp);
+    state.rng = seedrandom(state.sessionContext.timestamp);
 
   return state.rng();
 }