diff --git a/Assets/Scripts/GameManager.cs b/Assets/Scripts/GameManager.cs
index 472c79b78774ccdec9df922c96b8e4a08c759664..3bb9bba131a66433ef4750b84af6c813f8231177 100644
--- a/Assets/Scripts/GameManager.cs
+++ b/Assets/Scripts/GameManager.cs
@@ -123,7 +123,7 @@ public class GameManager : MonoBehaviour
     {
         while (true)
         {
-            AddMana(4.3f-Mathf.Log(LifeScript.TreeCount()));
+            AddMana(Mathf.Max(4.3f-Mathf.Log(LifeScript.TreeCount()),0f));
             yield return new WaitForSeconds(0.5f);
         }
     }