diff --git a/src/java/org/apache/poi/util/POILogFactory.java b/src/java/org/apache/poi/util/POILogFactory.java
index ba2551de7b..1e34ccd29b 100644
--- a/src/java/org/apache/poi/util/POILogFactory.java
+++ b/src/java/org/apache/poi/util/POILogFactory.java
@@ -35,7 +35,7 @@ public final class POILogFactory {
     /**
      * Map of POILogger instances, with classes as keys
      */
-    private static Map<String,POILogger> _loggers = new HashMap<String,POILogger>();
+    private static final Map<String,POILogger> _loggers = new HashMap<String,POILogger>();
 
     /**
      * A common instance of NullLogger, as it does nothing