1 files changed, 1 insertions, 1 deletions
diff --git a/server/src/main/java/com/vaadin/ui/TooltipConfiguration.java b/server/src/main/java/com/vaadin/ui/TooltipConfiguration.java
index b5af10961b..1bf9fd7b81 100644
--- a/server/src/main/java/com/vaadin/ui/TooltipConfiguration.java
+++ b/server/src/main/java/com/vaadin/ui/TooltipConfiguration.java
@@ -123,7 +123,7 @@ public interface TooltipConfiguration extends Serializable {
 }
 
 class TooltipConfigurationImpl implements TooltipConfiguration {
-    private UI ui;
+    private final UI ui;
 
     public TooltipConfigurationImpl(UI ui) {
         this.ui = ui;