diff --git a/CH.Bson.Test/Diff.cs b/CH.Bson.Test/Diff.cs
index 0987a03..8100ea9 100644
--- a/CH.Bson.Test/Diff.cs
+++ b/CH.Bson.Test/Diff.cs
@@ -270,7 +270,7 @@ public void DiffAFieldAddedAndAFieldModified()
 
             var expectedDiff = new BsonDocument
                 {
-                    {"+a:newField", 3},
+                    {"+a:newField", newFieldValue},
                     {
                         existingField, new BsonDocument
                             {
diff --git a/CH.Bson/Diff.cs b/CH.Bson/Diff.cs
index b0d16ef..b5b571c 100644
--- a/CH.Bson/Diff.cs
+++ b/CH.Bson/Diff.cs
@@ -55,7 +55,6 @@ public static BsonDocument Diff(this BsonDocument a, BsonDocument b)
         {
             var bson = ProcessDifferencesInDocument(a, b);
 
-
             bson.Add(ProcessFields(a, b));
 
             return bson;
@@ -73,16 +72,14 @@ private static BsonDocument ProcessDifferencesInDocument(this BsonDocument a, Bs
         {
             var bson = new BsonDocument();
 
-            if (!a.HasSameElementNamesAs(b))
+            foreach (var e in a.Where(e => !b.Contains(e.Name)))
+            {
+                bson.SetElement(new BsonElement("+a:" + e.Name, e.Value));
+            }
+
+            foreach (var e in b.Where(e => !a.Contains(e.Name)))
             {
-                foreach (var e in a.Where(e => !b.Contains(e.Name)))
-                {
-                    bson.SetElement(new BsonElement("+a:" + e.Name, e.Value));
-                }
-                foreach (var e in b.Where(e => !a.Contains(e.Name)))
-                {
-                    bson.SetElement(new BsonElement("+b:" + e.Name, e.Value));
-                }
+                bson.SetElement(new BsonElement("+b:" + e.Name, e.Value));
             }
 
             return bson;