diff --git a/winsup/cygwin/release/3.5.6 b/winsup/cygwin/release/3.5.6
new file mode 100644
index 0000000000..643d58e585
--- /dev/null
+++ b/winsup/cygwin/release/3.5.6
@@ -0,0 +1,5 @@
+Fixes:
+------
+
+- Fix zsh hang at startup.
+  Addresses: https://cygwin.com/pipermail/cygwin/2024-December/256954.html
diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc
index cf43aa9335..c2985277fc 100644
--- a/winsup/cygwin/sigproc.cc
+++ b/winsup/cygwin/sigproc.cc
@@ -751,10 +751,14 @@ sig_send (_pinfo *p, siginfo_t& si, _cygtls *tls)
       res = WriteFile (sendsig, leader, packsize, &nb, NULL);
       if (!res || packsize == nb)
 	break;
-      if (cygwait (NULL, 10, cw_sig_eintr) == WAIT_SIGNALED)
+      if (cygwait (NULL, 10, cw_sig_eintr) == WAIT_SIGNALED
+	  && pack.si.si_signo != __SIGFLUSHFAST)
 	_my_tls.call_signal_handler ();
       res = 0;
     }
+  /* Re-assert signal_arrived which has been cleared in cygwait(). */
+  if (_my_tls.sig)
+    _my_tls.set_signal_arrived ();
 
   if (!res)
     {
@@ -785,7 +789,16 @@ sig_send (_pinfo *p, siginfo_t& si, _cygtls *tls)
   if (wait_for_completion)
     {
       sigproc_printf ("Waiting for pack.wakeup %p", pack.wakeup);
-      rc = cygwait (pack.wakeup, WSSC);
+      do
+	{
+	  rc = cygwait (pack.wakeup, WSSC, cw_sig_eintr);
+	  if (rc == WAIT_SIGNALED && pack.si.si_signo != __SIGFLUSHFAST)
+	    _my_tls.call_signal_handler ();
+	}
+      while (rc != WAIT_OBJECT_0 && rc != WAIT_TIMEOUT);
+      /* Re-assert signal_arrived which has been cleared in cygwait(). */
+      if (_my_tls.sig)
+	_my_tls.set_signal_arrived ();
       ForceCloseHandle (pack.wakeup);
     }
   else
@@ -806,9 +819,6 @@ sig_send (_pinfo *p, siginfo_t& si, _cygtls *tls)
       rc = -1;
     }
 
-  if (wait_for_completion && si.si_signo != __SIGFLUSHFAST)
-    _my_tls.call_signal_handler ();
-
 out:
   if (communing && rc)
     {