diff -ru Python-2.7.13/Modules/signalmodule.c Python-2.7.13-fixed//Modules/signalmodule.c
--- Python-2.7.13/Modules/signalmodule.c	2016-12-17 21:05:07.000000000 +0100
+++ Python-2.7.13-fixed//Modules/signalmodule.c	2017-04-12 17:55:03.759805763 +0200
@@ -313,12 +313,13 @@
     }
     else
         func = signal_handler;
+    /* Check for pending signals before changing signal handler */
+    if (PyErr_CheckSignals()) return NULL;
     if (PyOS_setsig(sig_num, func) == SIG_ERR) {
         PyErr_SetFromErrno(PyExc_RuntimeError);
         return NULL;
     }
     old_handler = Handlers[sig_num].func;
-    Handlers[sig_num].tripped = 0;
     Py_INCREF(obj);
     Handlers[sig_num].func = obj;
     if (old_handler != NULL)