diff --git a/redo/deps.py b/redo/deps.py
index 0ce53d3..bc2909c 100644
--- a/redo/deps.py
+++ b/redo/deps.py
@@ -95,7 +95,7 @@ def isdirty(f, depth, max_changed,
         elif mode == 'm':
             sub = isdirty(f2, depth=depth + '  ',
                           max_changed=max(f.changed_runid,
-                                          f.checked_runid),
+                                          f.checked_runid or 0),
                           already_checked=already_checked,
                           is_checked=is_checked,
                           set_checked=set_checked,
diff --git a/redo/state.py b/redo/state.py
index 37b1856..667a3d8 100644
--- a/redo/state.py
+++ b/redo/state.py
@@ -278,7 +278,8 @@ class File(object):
         (self.id, self.name, self.is_generated, self.is_override,
          self.checked_runid, self.changed_runid, self.failed_runid,
          self.stamp, self.csum) = cols
-        if self.name == ALWAYS and self.changed_runid < env.v.RUNID:
+        if self.name == ALWAYS and (
+            self.changed_runid is None or self.changed_runid < env.v.RUNID):
             self.changed_runid = env.v.RUNID
 
     def __init__(self, fid=None, name=None, cols=None, allow_add=True):