diff --git a/cuburn/genome/blend.py b/cuburn/genome/blend.py
index 1b5079d..079f97c 100644
--- a/cuburn/genome/blend.py
+++ b/cuburn/genome/blend.py
@@ -55,7 +55,7 @@ def resolve(gdb, item):
         else:
             r = vs[-1]
         out[k] = r
-    return unflatten(out.items())
+    return unflatten(out)
 
 def _split_ref_id(s):
     sp = s.split('@')
diff --git a/cuburn/genome/util.py b/cuburn/genome/util.py
index e4afc29..daa02e7 100644
--- a/cuburn/genome/util.py
+++ b/cuburn/genome/util.py
@@ -32,12 +32,12 @@ def flatten(src):
                 yield '.'.join(ctx + (k,)), v
     return dict(go(src))
 
-def unflatten(kvlist):
+def unflatten(dct):
     """
     Given a flattened dict, return a nested dict, where every dot-separated
     key is converted into a sub-dict.
 
-    >>> (unflatten([('ab.xy.zw', 1), ('4', 5)) ==
+    >>> (unflatten({'ab.xy.zw': 1, '4': 5}) ==
     ...  {'ab': {'xy': {'zw': 1}}, '4': 5})
     True
     """
@@ -47,7 +47,7 @@ def unflatten(kvlist):
         else:
             go(d.setdefault(k[0], {}), k[1:], v)
     out = {}
-    for k, v in kvlist:
+    for k, v in dct.items():
         go(out, k.split('.'), v)
     return out