diff --git a/AppKit/CPCollectionView.j b/AppKit/CPCollectionView.j
index 3bd31a1a1..14c4dcc96 100644
--- a/AppKit/CPCollectionView.j
+++ b/AppKit/CPCollectionView.j
@@ -597,6 +597,10 @@
     if (![_selectionIndexes count])
         return;
 
+    if ([_delegate respondsToSelector:@selector(collectionView:canDragItemsAtIndexes:withEvent:)] &&
+        ![_delegate collectionView:self canDragItemsAtIndexes:_selectionIndexes withEvent:anEvent])
+        return;
+
     // Set up the pasteboard
     var dragTypes = [_delegate collectionView:self dragTypesForItemsAtIndexes:_selectionIndexes];
 
diff --git a/Foundation/CPProxy.j b/Foundation/CPProxy.j
index 28bf7c11a..2d5fba736 100644
--- a/Foundation/CPProxy.j
+++ b/Foundation/CPProxy.j
@@ -61,7 +61,7 @@
 - (void)forwardInvocation:(CPInvocation)anInvocation
 {
     [CPException raise:CPInvalidArgumentException
-                reason:@"-methodSignatureForSelector: called on abstract CPProxy class."];
+                reason:@"-forwardInvocation: called on abstract CPProxy class."];
 }
 
 // FIXME: This should be moved to the runtime?