diff --git a/src/viewer.js b/src/viewer.js
index 6d57d945..bc40160a 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -1011,6 +1011,9 @@ $.extend( $.Viewer.prototype, $.EventSource.prototype, $.ControlDock.prototype,
         if ( !tileSource ) {
             throw new Error( "No tile source provided as new layer." );
         }
+        if ( this.collectionMode ) {
+            throw new Error( "Layers not supported in collection mode." );
+        }
 
         function raiseAddLayerFailed( event ) {
              /**