diff --git a/Doc/library/faulthandler.rst b/Doc/library/faulthandler.rst
index 106da45..c0b6625 100644
--- a/Doc/library/faulthandler.rst
+++ b/Doc/library/faulthandler.rst
@@ -97,7 +97,8 @@
 .. function:: unregister(signum)
 
    Unregister a user signal: uninstall the handler of the *signum* signal
-   installed by :func:`register`.
+   installed by :func:`register`. Return ``True`` if the signal was registered,
+   ``False`` otherwise.
 
    Not available on Windows.
 
diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c
index 76cadf3..1132036 100644
--- a/Modules/faulthandler.c
+++ b/Modules/faulthandler.c
@@ -694,6 +694,9 @@
     if (!check_signum(signum))
         return NULL;
 
+    if (user_signals == NULL)
+        Py_RETURN_FALSE;
+
     user = &user_signals[signum];
     change = faulthandler_unregister(user, signum);
     return PyBool_FromLong(change);