diff --git a/src/components/WindowSideBarCollectionPanel.js b/src/components/WindowSideBarCollectionPanel.js
index 78b6f2b0c93def01ae376b1375a11acbf6adff7e..f480ec42ca2bda9e07da7cf56283f0745e57a9e4 100644
--- a/src/components/WindowSideBarCollectionPanel.js
+++ b/src/components/WindowSideBarCollectionPanel.js
@@ -31,7 +31,7 @@ export class WindowSideBarCollectionPanel extends Component {
 
     const behaviors = collection.getProperty('behavior');
 
-    if (Array.isArray(behaviors)) return collection.includes('multi-part');
+    if (Array.isArray(behaviors)) return behaviors.includes('multi-part');
 
     return behaviors === 'multi-part';
   }