diff --git a/deps.py b/deps.py
index 93063f9..173cd72 100644
--- a/deps.py
+++ b/deps.py
@@ -58,10 +58,15 @@ def isdirty(f, depth, max_changed,
             assert(mode in ('c','m'))
         if not f.csum:
             # f is a "normal" target: dirty f2 means f is instantly dirty
-            if dirty:
-                # if dirty==DIRTY, this means f is definitely dirty.
-                # if dirty==[...], it's a list of the uncertain children.
-                return dirty
+            if dirty == DIRTY:
+                # f2 is definitely dirty, so f definitely needs to
+                # redo.
+                return DIRTY
+            elif isinstance(dirty,list):
+                # our child f2 might be dirty, but it's not sure yet.  It's
+                # given us a list of targets we have to redo in order to
+                # be sure.
+                must_build += dirty
         else:
             # f is "checksummable": dirty f2 means f needs to redo,
             # but f might turn out to be clean after that (ie. our parent
@@ -83,6 +88,7 @@ def isdirty(f, depth, max_changed,
         # objects in the tree.  If we build all those, we can then
         # redo-ifchange f and it won't have any uncertainty next time.
         return must_build
+    debug('%s-- CLEAN\n' % (depth,))
 
     # if we get here, it's because the target is clean
     if f.is_override:
diff --git a/state.py b/state.py
index b9dd259..f5be070 100644
--- a/state.py
+++ b/state.py
@@ -200,6 +200,9 @@ class File(object):
         else:
             return self._init_from_idname(id, name)
 
+    def __repr__(self):
+        return "File(%r)" % (self.nicename(),)
+
     def refresh(self):
         self._init_from_idname(self.id, None)
 
diff --git a/t/660-stamp/.gitignore b/t/660-stamp/.gitignore
index ae5524f..f789dc9 100644
--- a/t/660-stamp/.gitignore
+++ b/t/660-stamp/.gitignore
@@ -4,3 +4,9 @@
 /inp
 /bob
 /usestamp2
+/a
+/b
+/ab
+/doing_ab
+/abc
+/doing_abc
diff --git a/t/660-stamp/a.do b/t/660-stamp/a.do
new file mode 100644
index 0000000..3bb0c39
--- /dev/null
+++ b/t/660-stamp/a.do
@@ -0,0 +1,3 @@
+redo-always
+echo a | redo-stamp
+echo a > $3
diff --git a/t/660-stamp/ab.do b/t/660-stamp/ab.do
new file mode 100644
index 0000000..751c007
--- /dev/null
+++ b/t/660-stamp/ab.do
@@ -0,0 +1,4 @@
+redo-ifchange a b
+echo "doing ab" >&2
+echo ab >$3
+touch doing_ab
diff --git a/t/660-stamp/abc.do b/t/660-stamp/abc.do
new file mode 100644
index 0000000..d97d9e1
--- /dev/null
+++ b/t/660-stamp/abc.do
@@ -0,0 +1,4 @@
+redo-ifchange ab c
+echo "doing abc" >&2
+echo abc >$3
+touch doing_abc
diff --git a/t/660-stamp/b.do b/t/660-stamp/b.do
new file mode 100644
index 0000000..4326b6e
--- /dev/null
+++ b/t/660-stamp/b.do
@@ -0,0 +1,3 @@
+redo-always
+echo b | redo-stamp
+echo b > $3
diff --git a/t/660-stamp/c b/t/660-stamp/c
new file mode 100644
index 0000000..e69de29
diff --git a/t/660-stamp/clean.do b/t/660-stamp/clean.do
index 3bdd118..80faf52 100644
--- a/t/660-stamp/clean.do
+++ b/t/660-stamp/clean.do
@@ -1 +1 @@
-rm -f *.log usestamp usestamp2 stampy inp bob *~ .*~
+rm -f *.log usestamp usestamp2 stampy inp bob *~ .*~ a b ab doing_ab
diff --git a/t/660-stamp/stamptest.do b/t/660-stamp/stamptest.do
index 51bb3f1..6e318ed 100644
--- a/t/660-stamp/stamptest.do
+++ b/t/660-stamp/stamptest.do
@@ -70,3 +70,16 @@ redo-ifchange usestamp usestamp2
 rm -f stampy
 redo-ifchange stampy
 [ "$(wc -l <stampy.log)" -eq 6 ] || exit 74
+
+# check that a target that depends on two stamped targets (that are marked as
+# always built) won't be redone if neither stamped targets changes
+../flush-cache
+redo-ifchange abc
+rm -f doing_ab doing_abc
+redo-ifchange abc
+[ ! -f doing_ab ] || exit 92
+[ ! -f doing_abc ] || exit 93
+../flush-cache
+redo-ifchange abc
+[ ! -f doing_ab ] || exit 94
+[ ! -f doing_abc ] || exit 95