diff --git a/builder.py b/builder.py
index 6240435..a7d4294 100644
--- a/builder.py
+++ b/builder.py
@@ -86,7 +86,11 @@ class BuildJob:
     def start(self):
         assert(self.lock.owned)
         try:
-            dirty = self.shouldbuildfunc(self.t)
+            try:
+                dirty = self.shouldbuildfunc(self.t)
+            except state.CyclicDependencyError:
+                err('cyclic dependency while checking %s\n' % _nice(self.t))
+                raise ImmediateReturn(208)
             if not dirty:
                 # target doesn't need to be built; skip the whole task
                 return self._after2(0)
diff --git a/deps.py b/deps.py
index 173cd72..dd658c5 100644
--- a/deps.py
+++ b/deps.py
@@ -6,8 +6,15 @@ CLEAN = 0
 DIRTY = 1
 
 def isdirty(f, depth, max_changed,
+            already_checked,
             is_checked=state.File.is_checked,
             set_checked=state.File.set_checked_save):
+    if f.id in already_checked:
+        raise state.CyclicDependencyError()
+    # make a copy of the list, so upon returning, our parent's copy
+    # is unaffected
+    already_checked = list(already_checked) + [f.id]
+
     if vars.DEBUG >= 1:
         debug('%s?%s\n' % (depth, f.nicename()))
 
@@ -50,6 +57,7 @@ def isdirty(f, depth, max_changed,
             sub = isdirty(f2, depth = depth + '  ',
                           max_changed = max(f.changed_runid,
                                             f.checked_runid),
+                          already_checked=already_checked,
                           is_checked=is_checked, set_checked=set_checked)
             if sub:
                 debug('%s-- DIRTY (sub)\n' % depth)
diff --git a/redo-ifchange.py b/redo-ifchange.py
index c1345c6..ee6dd83 100755
--- a/redo-ifchange.py
+++ b/redo-ifchange.py
@@ -12,7 +12,8 @@ def should_build(t):
     f = state.File(name=t)
     if f.is_failed():
         raise builder.ImmediateReturn(32)
-    dirty = deps.isdirty(f, depth = '', max_changed = vars.RUNID)
+    dirty = deps.isdirty(f, depth = '', max_changed = vars.RUNID,
+                         already_checked=[])
     return dirty==[f] and deps.DIRTY or dirty
 
 
diff --git a/redo-ood.py b/redo-ood.py
index 433d7ea..250aad1 100755
--- a/redo-ood.py
+++ b/redo-ood.py
@@ -24,5 +24,6 @@ def set_checked(f):
 for f in state.files():
     if f.is_generated and f.read_stamp() != state.STAMP_MISSING:
         if deps.isdirty(f, depth='', max_changed=vars.RUNID,
+                        already_checked=[],
                         is_checked=is_checked, set_checked=set_checked):
             print f.nicename()
diff --git a/state.py b/state.py
index 7f24728..dd490db 100644
--- a/state.py
+++ b/state.py
@@ -365,7 +365,7 @@ class Lock:
         assert(not self.owned)
         if str(self.fid) in vars.get_locks():
             # Lock already held by parent: cyclic dependence
-            raise CyclicDependencyError
+            raise CyclicDependencyError()
         fcntl.lockf(self.lockfile, fcntl.LOCK_EX, 0, 0)
         self.owned = True