diff --git a/redo/jobserver.py b/redo/jobserver.py
index 800f5d3..86eea3c 100644
--- a/redo/jobserver.py
+++ b/redo/jobserver.py
@@ -142,8 +142,10 @@ def release_mine():
     _release(1)
 
 
+class TimeoutError(Exception): pass
+
 def _timeout(sig, frame):
-    pass
+    raise TimeoutError()
 
 
 # We make the pipes use the first available fd numbers starting at startfd.
@@ -171,11 +173,13 @@ def _try_read(fd, n):
         return None  # try again
     # ok, the socket is readable - but some other process might get there
     # first.  We have to set an alarm() in case our read() gets stuck.
-    oldh = signal.signal(signal.SIGALRM, _timeout)
     try:
+        oldh = signal.signal(signal.SIGALRM, _timeout)
         signal.setitimer(signal.ITIMER_REAL, 0.01, 0.01)  # emergency fallback
         try:
             b = os.read(fd, 1)
+        except TimeoutError:
+            return None  # try again
         except OSError as e:
             if e.errno in (errno.EAGAIN, errno.EINTR):
                 # interrupted or it was nonblocking