diff --git a/src/main/java/sma/SEIRS_SMA.java b/src/main/java/sma/SEIRS_SMA.java
index 86216b54e1f0ca3e99dddec8142fce9f6ea73854..d24884d8071fe22df7aab709cbd8dfa9051a99aa 100644
--- a/src/main/java/sma/SEIRS_SMA.java
+++ b/src/main/java/sma/SEIRS_SMA.java
@@ -34,7 +34,7 @@ public class SEIRS_SMA implements SMA{
     private StatisticsCanvas statisticsCanvas;
     private DisplaySquaredEnvironment display;
     private Random r;
-    private FrameBuilder fb = new FrameBuilder();
+    private final FrameBuilder fb = new FrameBuilder();
 
     private HashMap<String,Integer> stats;