diff --git a/Source/Collections/MultiDictionary.Interfaces.cs b/Source/Collections/MultiDictionary.Interfaces.cs
index c5b0794..86c1a1e 100644
--- a/Source/Collections/MultiDictionary.Interfaces.cs
+++ b/Source/Collections/MultiDictionary.Interfaces.cs
@@ -241,6 +241,13 @@ namespace Nuclex.Support.Collections {
       return this.typedDictionary.GetEnumerator();
     }
 
+    /// <summary>Removes the specified key/value pair from the dictionary</summary>
+    /// <param name="item">Key/value pair that will be removed</param>
+    /// <returns>True if the key/value pair was contained in the dictionary</returns>
+    int ICollection<KeyValuePair<TKey, ICollection<TValue>>>.Count {
+      get { return this.typedDictionary.Count; }
+    }
+
     #endregion // ICollection<KeyValuePair<TKey, ICollection<TValue>>> implementation
 
   }
diff --git a/Source/Collections/MultiDictionary.Test.cs b/Source/Collections/MultiDictionary.Test.cs
index 15a1fa4..19310bc 100644
--- a/Source/Collections/MultiDictionary.Test.cs
+++ b/Source/Collections/MultiDictionary.Test.cs
@@ -139,6 +139,21 @@ namespace Nuclex.Support.Collections {
       );
     }
 
+    /// <summary>
+    ///   Verifies that the Count property returns the number of unique keys if it is called
+    ///   on the collection-of-collections interface implemented by the multi dictionary
+    /// </summary>
+    [Test]
+    public void CollectionOfCollectionCountIsUniqueKeyCount() {
+      var dictionary = new MultiDictionary<int, string>();
+      dictionary.Add(10, "ten");
+      dictionary.Add(10, "zehn");
+
+      Assert.AreEqual(2, dictionary.Count);
+      var collectionOfCollections = (ICollection<KeyValuePair<int, ICollection<string>>>)dictionary;
+      Assert.AreEqual(1, collectionOfCollections.Count);
+    }
+
   }
 
 } // namespace Nuclex.Support.Collections