diff -up bash-4.1/sig.h.signal bash-4.1/sig.h

--- bash-4.1/sig.h.signal	2009-01-04 20:32:41.000000000 +0100

+++ bash-4.1/sig.h	2012-08-28 11:19:14.920224571 +0200

@@ -96,6 +96,8 @@ do { \

   sigprocmask (SIG_BLOCK, &nvar, &ovar); \

 } while (0)

+#define UNBLOCK_SIGNAL(ovar) sigprocmask (SIG_SETMASK, &ovar, (sigset_t *)NULL)

+

 #if defined (HAVE_POSIX_SIGNALS)

 #  define BLOCK_CHILD(nvar, ovar) \

 	BLOCK_SIGNAL (SIGCHLD, nvar, ovar)

diff -up bash-4.1/trap.c.signal bash-4.1/trap.c

--- bash-4.1/trap.c.signal	2009-10-10 23:21:44.000000000 +0200

+++ bash-4.1/trap.c	2012-08-28 10:58:14.746345797 +0200

@@ -516,6 +516,8 @@ set_signal (sig, string)

      int sig;

      char *string;

 {

+  sigset_t set, oset;

+

   if (SPECIAL_TRAP (sig))

     {

       change_signal (sig, savestring (string));

@@ -546,9 +548,10 @@ set_signal (sig, string)

      environment in which it is safe to do so. */

   if ((sigmodes[sig] & SIG_NO_TRAP) == 0)

     {

-      set_signal_handler (sig, SIG_IGN);

+      BLOCK_SIGNAL (sig, set, oset);

       change_signal (sig, savestring (string));

       set_signal_handler (sig, trap_handler);

+      UNBLOCK_SIGNAL (oset);

     }

   else

     change_signal (sig, savestring (string));