diff --git a/ffmpeg/_utils.py b/ffmpeg/_utils.py
index 9b575a0..d3acc4c 100644
--- a/ffmpeg/_utils.py
+++ b/ffmpeg/_utils.py
@@ -27,6 +27,7 @@ def get_hash(item):
     repr_ = _recursive_repr(item).encode('utf-8')
     return hashlib.md5(repr_).hexdigest()
 
+
 def get_hash_int(item):
     return int(get_hash(item), base=16)
 
@@ -41,3 +42,8 @@ def escape_chars(text, chars):
     for ch in chars:
         text = text.replace(ch, '\\' + ch)
     return text
+
+
+def sort_ordereddict(d):
+    for key in sorted(d.keys()):
+        d.move_to_end(key)
diff --git a/ffmpeg/dag.py b/ffmpeg/dag.py
index 86c695f..7e6b91e 100644
--- a/ffmpeg/dag.py
+++ b/ffmpeg/dag.py
@@ -1,6 +1,6 @@
 from __future__ import unicode_literals
 
-from ._utils import get_hash, get_hash_int
+from ._utils import get_hash, get_hash_int, sort_ordereddict
 from builtins import object
 from collections import namedtuple, OrderedDict
 
@@ -177,7 +177,6 @@ def topo_sort(downstream_nodes):
 
     # Sort outgoing edge maps by upstream label
     for map in outgoing_edge_maps.values():
-        for label in sorted(map.keys()):
-            map.move_to_end(label)
+        sort_ordereddict(map)
 
     return sorted_nodes, outgoing_edge_maps