diff --git a/pyproject.toml b/pyproject.toml
index 5d9cbb7..2c1fb21 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "vizing"
-version = "0.2.1"
+version = "0.2.1.9000"
 description = "Constraint-based list-colouring in Python."
 authors = ["Matthew Henderson <matthew.james.henderson@gmail.com>"]
 readme = "README.md"
diff --git a/src/vizing/__init__.py b/src/vizing/__init__.py
index 4468644..c185180 100644
--- a/src/vizing/__init__.py
+++ b/src/vizing/__init__.py
@@ -40,8 +40,8 @@ def edge_list_colouring_problem(G, directed = False):
     P.addVariable(edge, G.edges[edge]['permissible'])
   if(directed):
     for node in G.nodes():
-      P.addConstraint(ct.AllDifferentConstraint(), [x for x in G.out_edges(node)])
-      P.addConstraint(ct.AllDifferentConstraint(), [x for x in G.in_edges(node)])
+      P.addConstraint(ct.AllDifferentConstraint(), G.out_edges(node))
+      P.addConstraint(ct.AllDifferentConstraint(), G.in_edges(node))
     else:
       for node in G.nodes():
         P.addConstraint(ct.AllDifferentConstraint(), [tuple(sorted(x)) for x in G.edges(node)])