diff --git a/plugins/org.eclipse.ocl/src/org/eclipse/ocl/util/CollectionUtil.java b/plugins/org.eclipse.ocl/src/org/eclipse/ocl/util/CollectionUtil.java
index 24374b8..c38fee0 100644
--- a/plugins/org.eclipse.ocl/src/org/eclipse/ocl/util/CollectionUtil.java
+++ b/plugins/org.eclipse.ocl/src/org/eclipse/ocl/util/CollectionUtil.java
@@ -468,45 +468,29 @@
         // Note: As OCL 2.3 (OMG 10-11-42) section A.2.5.8 fails to specify how to
         // flatten an OrderedSet, we choose to flatten it into an OrderedSet
         // represented by a LinkedHashSet.
-        Collection<?> result = self;
-        
-        for (;;) {
-            if (result.isEmpty()) {
+        Collection<Object> result = null;
+        for (Object object : self) {
+        	if (object instanceof Collection<?>) {
+                result = createNewCollectionOfSameKind(self);
                 break;
-            }
-            
-            Iterator<?> it = result.iterator();
-            Object object = it.next();
-    
-            // if the element type is not a collection type, the result is the
-            // current collection.
-            if (!(object instanceof Collection<?>)) {
-                break;
-            }
-    
-            Collection<Object> newResult = null;
-            if (result instanceof Bag<?>) {
-                newResult = createNewBag();
-            } else if (result instanceof Set<?>) {
-                newResult = createNewSet();
-            } else {
-                // Sequence
-                newResult = createNewSequence();
-            }
-            
-            // the element type is a collection type -- flatten one level
-            newResult.addAll((Collection<?>) object);
-            while (it.hasNext()) {
-                newResult.addAll((Collection<?>) it.next());
-            }
-            
-            result = newResult;
-            // loop until the result is empty or the first element is not a
-            // collection
+        	}
         }
-        
+        if (result == null) {			// Already flat
+        	return self;
+        }
+        flattenRecursion(result, self);
         return result;
     }
+    private static void flattenRecursion(Collection<Object> result, Collection<?> children) {
+        for (Object object : children) {
+        	if (object instanceof Collection<?>) {
+                flattenRecursion(result, (Collection<?>) object);
+        	}
+        	else {
+        		result.add(object);
+        	}
+        }
+    }
 
     /**
      * Obtains the type of the flattened form of the specified collection type.
diff --git a/tests/org.eclipse.ocl.ecore.tests/src/org/eclipse/ocl/ecore/tests/CollectionsTest.java b/tests/org.eclipse.ocl.ecore.tests/src/org/eclipse/ocl/ecore/tests/CollectionsTest.java
index 02fd7c5..96fa628 100644
--- a/tests/org.eclipse.ocl.ecore.tests/src/org/eclipse/ocl/ecore/tests/CollectionsTest.java
+++ b/tests/org.eclipse.ocl.ecore.tests/src/org/eclipse/ocl/ecore/tests/CollectionsTest.java
@@ -403,7 +403,7 @@
 			assertTrue(check(helper,
 				"",
 				"OrderedSet{Sequence{'a', 'b'}, Sequence{'b', 'c', 'd'}}->flatten()" +
-					" = Set{'b', 'c', 'a', 'd'}"));
+					" = OrderedSet{'a', 'b', 'c', 'd'}"));
 
 			assertTrue(check(helper,
 				"",
@@ -500,7 +500,7 @@
 
 			assertTrue(check(helper, "",
 				"OrderedSet{OrderedSet{}, OrderedSet{}}->flatten()" +
-					" = Set{}"));
+					" = OrderedSet{}"));
 
 			assertTrue(check(helper, "",
 				"Sequence{Sequence{}, Sequence{}}->flatten()" +
@@ -529,7 +529,7 @@
 			assertTrue(check(helper,
 				"",
 				"OrderedSet{Sequence{Set{'a'}, Set{'b'}}, Sequence{Set{'b', 'c'}, Set{'d'}}}->flatten()" +
-					" = Set{'b', 'c', 'a', 'd'}"));
+					" = OrderedSet{'a', 'b', 'c', 'd'}"));
 
 			assertTrue(check(helper,
 				"",
@@ -560,7 +560,7 @@
 			assertTrue(check(helper,
 				"",
 				"OrderedSet{OrderedSet{Sequence{}, Sequence{}}, OrderedSet{Sequence{}, Sequence{}}}->flatten()" +
-					" = Set{}"));
+					" = OrderedSet{}"));
 
 			assertTrue(check(helper,
 				"",
diff --git a/tests/org.eclipse.ocl.uml.tests/src/org/eclipse/ocl/uml/tests/CollectionsTest.java b/tests/org.eclipse.ocl.uml.tests/src/org/eclipse/ocl/uml/tests/CollectionsTest.java
index 13c088f..ea0e574 100644
--- a/tests/org.eclipse.ocl.uml.tests/src/org/eclipse/ocl/uml/tests/CollectionsTest.java
+++ b/tests/org.eclipse.ocl.uml.tests/src/org/eclipse/ocl/uml/tests/CollectionsTest.java
@@ -394,7 +394,7 @@
             assertTrue(check(helper,
                 "",
                 "OrderedSet{Sequence{'a', 'b'}, Sequence{'b', 'c', 'd'}}->flatten()" +
-                    " = Set{'b', 'c', 'a', 'd'}"));
+                    " = OrderedSet{'a', 'b', 'c', 'd'}"));
 
             assertTrue(check(helper,
                 "",