diff --git a/boltons/debugutils.py b/boltons/debugutils.py
index 5ac4f0f..27d9d80 100644
--- a/boltons/debugutils.py
+++ b/boltons/debugutils.py
@@ -1,14 +1,18 @@
 # -*- coding: utf-8 -*-
 
 
-def pdb_on_signal(signal=None):
+def pdb_on_signal(signalnum=None):
     import pdb
     import signal
-    if not signal:
-        signal = signal.SIGINT
+    if not signalnum:
+        signalnum = signal.SIGINT
+
+    old_handler = signal.getsignal(signalnum)
 
     def pdb_int_handler(sig, frame):
+        signal.signal(signalnum, old_handler)
         pdb.set_trace()
+        pdb_on_signal(signalnum)  # use 'u' to find your code and 'h' for help
 
-    signal.signal(signal.SIGINT, pdb_int_handler)
+    signal.signal(signalnum, pdb_int_handler)
     return