Index: core/src/org/netbeans/core/NbSheet.java
@@ -124,7 +124,11 @@
         setLayout (new BorderLayout ());
         add(propertySheet, BorderLayout.CENTER);
 
-        setIcon (Utilities.loadImage("org/netbeans/core/resources/frames/properties.gif")); // NOI18N
+// <> png instead of gif
+//        setIcon (Utilities.loadImage("org/netbeans/core/resources/frames/properties.gif")); // NOI18N
+// ====
+        setIcon (Utilities.loadImage("org/netbeans/core/resources/frames/properties.png")); // NOI18N
+// </>
 
         // #36738 Component has to have a name from begining.
         updateTitle();