diff --git a/src/Main/Core/Project/Src/Util/CommandWrapper.cs b/src/Main/Core/Project/Src/Util/CommandWrapper.cs
index 3d42363f56..70009c5366 100644
--- a/src/Main/Core/Project/Src/Util/CommandWrapper.cs
+++ b/src/Main/Core/Project/Src/Util/CommandWrapper.cs
@@ -160,6 +160,8 @@ namespace ICSharpCode.Core
 		
 		public event EventHandler CanExecuteChanged {
 			add {
+				if (value == null)
+					return;
 				if (conditions.Count > 0 && RegisterConditionRequerySuggestedHandler != null)
 					RegisterConditionRequerySuggestedHandler(value);
 				
@@ -169,6 +171,8 @@ namespace ICSharpCode.Core
 					canExecuteChangedHandlersToRegisterOnCommand.Add(value);
 			}
 			remove {
+				if (value == null)
+					return;
 				if (conditions.Count > 0 && UnregisterConditionRequerySuggestedHandler != null)
 					UnregisterConditionRequerySuggestedHandler(value);
 				
diff --git a/src/Main/Core/Project/Src/Util/WeakCollection.cs b/src/Main/Core/Project/Src/Util/WeakCollection.cs
index c393483db4..c6abeb3f50 100644
--- a/src/Main/Core/Project/Src/Util/WeakCollection.cs
+++ b/src/Main/Core/Project/Src/Util/WeakCollection.cs
@@ -61,21 +61,6 @@ namespace ICSharpCode.Core
 			CheckNoEnumerator();
 		}
 		
-		/// <summary>
-		/// Checks if the collection contains an item. Runtime: O(n).
-		/// </summary>
-		public bool Contains(T item)
-		{
-			if (item == null)
-				throw new ArgumentNullException("item");
-			CheckNoEnumerator();
-			foreach (T element in this) {
-				if (item.Equals(element))
-					return true;
-			}
-			return false;
-		}
-		
 		/// <summary>
 		/// Removes an element from the collection. Returns true if the item is found and removed,
 		/// false when the item is not found.
@@ -84,13 +69,14 @@ namespace ICSharpCode.Core
 		public bool Remove(T item)
 		{
 			if (item == null)
-				throw new ArgumentNullException("item");
+				return false;
 			CheckNoEnumerator();
+			var comparer = EqualityComparer<T>.Default;
 			for (int i = 0; i < innerList.Count;) {
 				T element = (T)innerList[i].Target;
 				if (element == null) {
 					RemoveAt(i);
-				} else if (element == item) {
+				} else if (comparer.Equals(element, item)) {
 					RemoveAt(i);
 					return true;
 				} else {