diff --git a/pyecoreocl/compiler.py b/pyecoreocl/compiler.py
index 32686ba..f87043a 100644
--- a/pyecoreocl/compiler.py
+++ b/pyecoreocl/compiler.py
@@ -290,7 +290,7 @@ def call_rule(fun):
 
 
 @call_rule
-def rule_collect(emitter, ctx):
+def rule_collect_nested(emitter, ctx):
     emitter.inline("(")
     emitter.visit(ctx.argExp().oclExp())
     variables = [arg.text for arg in ctx.argExp().varnames]
@@ -304,6 +304,21 @@ def rule_collect(emitter, ctx):
     emitter.inline(")")
 
 
+@call_rule
+def rule_collect(emitter, ctx):
+    emitter.inline("ocl.flatten(")
+    emitter.visit(ctx.argExp().oclExp())
+    variables = [arg.text for arg in ctx.argExp().varnames]
+    emitter.inline(f" for {', '.join(variables)} in ")
+    if len(variables) > 1:
+        emitter.inline("itertools.combinations_with_replacement(")
+        emitter.visit(ctx.expression)
+        emitter.inline(f", {len(variables)})")
+    else:
+        emitter.visit(ctx.expression)
+    emitter.inline(")")
+
+
 @call_rule
 def rule_for_all(emitter, ctx):
     emitter.inline(f"all(")
diff --git a/pyecoreocl/runtime.py b/pyecoreocl/runtime.py
index d42e2f6..3ec7bd1 100644
--- a/pyecoreocl/runtime.py
+++ b/pyecoreocl/runtime.py
@@ -11,7 +11,17 @@ def is_unique(lst):
     seen = []
     return not any(i in seen or seen.append(i) for i in lst)
 
+
 def geta(o, attr):
     if isinstance(o, Iterable):
         return (getattr(e, attr) for e in o)
-    return getattr(o, attr)
\ No newline at end of file
+    return getattr(o, attr)
+
+
+def flatten(items):
+    for x in items:
+        if isinstance(x, Iterable) and not isinstance(x, (str, bytes)):
+            for sub_x in flatten(x):
+                yield sub_x
+        else:
+            yield x
diff --git a/tests/test_collection_lib.py b/tests/test_collection_lib.py
index d308152..644d6a7 100644
--- a/tests/test_collection_lib.py
+++ b/tests/test_collection_lib.py
@@ -49,6 +49,23 @@ def test__collect():
     l = !Sequence{Tuple{value=3}, Tuple{value=4}, Tuple{value='stuff'}}!
     assert !l->collect(e | e.value)->asSequence()! == [3, 4, "stuff"]
 
+    l = [3, 4, 5]
+    assert !l->collect(e: int | Sequence{e})->asSequence()! == [3, 4, 5]
+
+
+def test__collect_nested():
+    l = [3, 4, 5]
+    assert !l->collectNested(e: int | e + 1)->asSequence()! == [4, 5, 6]
+
+    l = !Sequence{Tuple{value=3}, Tuple{value=4}, Tuple{value='stuff'}}!
+    assert !l->collectNested(e | e.value)->asSequence()! == [3, 4, "stuff"]
+
+    l = [3, 4, 5]
+    assert !l->collectNested(e: int | Sequence{e})->asSequence()! == [[3], [4], [5]]
+
+    l = [3, 4, 5]
+    assert !l->collectNested(e: int | Sequence{Sequence{e}})->asSequence()! == [[[3]], [[4]], [[5]]]
+
 
 def test__any():
     l = [3, 4, 5]