diff --git a/Lib/test/test_signal.py b/Lib/test/test_signal.py
index 7ce89f6..354c3fd 100644
--- a/Lib/test/test_signal.py
+++ b/Lib/test/test_signal.py
@@ -943,6 +943,10 @@
         self.assertRaises(OSError, signal.pthread_sigmask, 1700, [])
         with self.assertRaises(ValueError):
             signal.pthread_sigmask(signal.SIG_BLOCK, [signal.NSIG])
+        with self.assertRaises(ValueError):
+            signal.pthread_sigmask(signal.SIG_BLOCK, [0])
+        with self.assertRaises(ValueError):
+            signal.pthread_sigmask(signal.SIG_BLOCK, [1<<1000])
 
     @unittest.skipUnless(hasattr(signal, 'pthread_sigmask'),
                          'need signal.pthread_sigmask()')
diff --git a/Modules/clinic/signalmodule.c.h b/Modules/clinic/signalmodule.c.h
index eca2da1..4d7ac38 100644
--- a/Modules/clinic/signalmodule.c.h
+++ b/Modules/clinic/signalmodule.c.h
@@ -278,17 +278,17 @@
     {"pthread_sigmask", (PyCFunction)signal_pthread_sigmask, METH_FASTCALL, signal_pthread_sigmask__doc__},
 
 static PyObject *
-signal_pthread_sigmask_impl(PyObject *module, int how, PyObject *mask);
+signal_pthread_sigmask_impl(PyObject *module, int how, sigset_t mask);
 
 static PyObject *
 signal_pthread_sigmask(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     int how;
-    PyObject *mask;
+    sigset_t mask;
 
-    if (!_PyArg_ParseStack(args, nargs, "iO:pthread_sigmask",
-        &how, &mask)) {
+    if (!_PyArg_ParseStack(args, nargs, "iO&:pthread_sigmask",
+        &how, _Py_Sigset_Converter, &mask)) {
         goto exit;
     }
     return_value = signal_pthread_sigmask_impl(module, how, mask);
@@ -339,6 +339,24 @@
 #define SIGNAL_SIGWAIT_METHODDEF    \
     {"sigwait", (PyCFunction)signal_sigwait, METH_O, signal_sigwait__doc__},
 
+static PyObject *
+signal_sigwait_impl(PyObject *module, sigset_t sigset);
+
+static PyObject *
+signal_sigwait(PyObject *module, PyObject *arg)
+{
+    PyObject *return_value = NULL;
+    sigset_t sigset;
+
+    if (!PyArg_Parse(arg, "O&:sigwait", _Py_Sigset_Converter, &sigset)) {
+        goto exit;
+    }
+    return_value = signal_sigwait_impl(module, sigset);
+
+exit:
+    return return_value;
+}
+
 #endif /* defined(HAVE_SIGWAIT) */
 
 #if (defined(HAVE_SIGFILLSET) || defined(MS_WINDOWS))
@@ -379,6 +397,24 @@
 #define SIGNAL_SIGWAITINFO_METHODDEF    \
     {"sigwaitinfo", (PyCFunction)signal_sigwaitinfo, METH_O, signal_sigwaitinfo__doc__},
 
+static PyObject *
+signal_sigwaitinfo_impl(PyObject *module, sigset_t sigset);
+
+static PyObject *
+signal_sigwaitinfo(PyObject *module, PyObject *arg)
+{
+    PyObject *return_value = NULL;
+    sigset_t sigset;
+
+    if (!PyArg_Parse(arg, "O&:sigwaitinfo", _Py_Sigset_Converter, &sigset)) {
+        goto exit;
+    }
+    return_value = signal_sigwaitinfo_impl(module, sigset);
+
+exit:
+    return return_value;
+}
+
 #endif /* defined(HAVE_SIGWAITINFO) */
 
 #if defined(HAVE_SIGTIMEDWAIT)
@@ -395,19 +431,18 @@
     {"sigtimedwait", (PyCFunction)signal_sigtimedwait, METH_FASTCALL, signal_sigtimedwait__doc__},
 
 static PyObject *
-signal_sigtimedwait_impl(PyObject *module, PyObject *sigset,
+signal_sigtimedwait_impl(PyObject *module, sigset_t sigset,
                          PyObject *timeout_obj);
 
 static PyObject *
 signal_sigtimedwait(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    PyObject *sigset;
+    sigset_t sigset;
     PyObject *timeout_obj;
 
-    if (!_PyArg_UnpackStack(args, nargs, "sigtimedwait",
-        2, 2,
-        &sigset, &timeout_obj)) {
+    if (!_PyArg_ParseStack(args, nargs, "O&O:sigtimedwait",
+        _Py_Sigset_Converter, &sigset, &timeout_obj)) {
         goto exit;
     }
     return_value = signal_sigtimedwait_impl(module, sigset, timeout_obj);
@@ -499,4 +534,4 @@
 #ifndef SIGNAL_PTHREAD_KILL_METHODDEF
     #define SIGNAL_PTHREAD_KILL_METHODDEF
 #endif /* !defined(SIGNAL_PTHREAD_KILL_METHODDEF) */
-/*[clinic end generated code: output=f35d79e0cfee3f1b input=a9049054013a1b77]*/
+/*[clinic end generated code: output=549f0efdc7405834 input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 4ac6e76..a9b3917 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -1267,6 +1267,65 @@
 #endif
 }
 
+#ifdef HAVE_SIGSET_T
+/* Convert an iterable of integers to a sigset.
+   Return 1 on success, return 0 and raise an exception on error. */
+int
+_Py_Sigset_Converter(PyObject *obj, void *addr)
+{
+    sigset_t *mask = (sigset_t *)addr;
+    PyObject *iterator, *item;
+    long signum;
+    int overflow;
+
+    if (sigemptyset(mask)) {
+        /* Probably only if mask == NULL. */
+        PyErr_SetFromErrno(PyExc_OSError);
+        return 0;
+    }
+
+    iterator = PyObject_GetIter(obj);
+    if (iterator == NULL) {
+        return 0;
+    }
+
+    while ((item = PyIter_Next(iterator)) != NULL) {
+        signum = PyLong_AsLongAndOverflow(item, &overflow);
+        Py_DECREF(item);
+        if (signum <= 0 || signum >= NSIG) {
+            if (overflow || signum != -1 || !PyErr_Occurred()) {
+                PyErr_Format(PyExc_ValueError,
+                             "signal number %ld out of range", signum);
+            }
+            goto error;
+        }
+        if (sigaddset(mask, (int)signum)) {
+            if (errno != EINVAL) {
+                /* Probably impossible */
+                PyErr_SetFromErrno(PyExc_OSError);
+                goto error;
+            }
+            /* For backwards compatibility, allow idioms such as
+             * `range(1, NSIG)` but warn about invalid signal numbers
+             */
+            const char msg[] =
+                "invalid signal number %ld, please use valid_signals()";
+            if (PyErr_WarnFormat(PyExc_RuntimeWarning, 1, msg, signum)) {
+                goto error;
+            }
+        }
+    }
+    if (!PyErr_Occurred()) {
+        Py_DECREF(iterator);
+        return 1;
+    }
+
+error:
+    Py_DECREF(iterator);
+    return 0;
+}
+#endif /* HAVE_SIGSET_T */
+
 #ifdef MS_WINDOWS
 
 static int
diff --git a/Modules/posixmodule.h b/Modules/posixmodule.h
index 1ec1833..1e00562 100644
--- a/Modules/posixmodule.h
+++ b/Modules/posixmodule.h
@@ -17,8 +17,17 @@
 PyAPI_FUNC(int) _Py_Uid_Converter(PyObject *, void *);
 PyAPI_FUNC(int) _Py_Gid_Converter(PyObject *, void *);
 #endif /* MS_WINDOWS */
+
+#if defined(PYPTHREAD_SIGMASK) || defined(HAVE_SIGWAIT) || \
+        defined(HAVE_SIGWAITINFO) || defined(HAVE_SIGTIMEDWAIT)
+# define HAVE_SIGSET_T
 #endif
 
+#ifdef HAVE_SIGSET_T
+PyAPI_FUNC(int) _Py_Sigset_Converter(PyObject *, void *);
+#endif /* HAVE_SIGSET_T */
+#endif /* Py_LIMITED_API */
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index 003bbb6..818df7d 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -59,6 +59,14 @@
 [clinic start generated code]*/
 /*[clinic end generated code: output=da39a3ee5e6b4b0d input=b0301a3bde5fe9d3]*/
 
+/*[python input]
+
+class sigset_t_converter(CConverter):
+    type = 'sigset_t'
+    converter = '_Py_Sigset_Converter'
+
+[python start generated code]*/
+/*[python end generated code: output=da39a3ee5e6b4b0d input=b5689d14466b6823]*/
 
 /*
    NOTES ON THE INTERACTION BETWEEN SIGNALS AND THREADS
@@ -808,69 +816,6 @@
 
 #endif
 
-#if defined(PYPTHREAD_SIGMASK) || defined(HAVE_SIGWAIT) || \
-        defined(HAVE_SIGWAITINFO) || defined(HAVE_SIGTIMEDWAIT)
-/* Convert an iterable to a sigset.
-   Return 0 on success, return -1 and raise an exception on error. */
-
-static int
-iterable_to_sigset(PyObject *iterable, sigset_t *mask)
-{
-    int result = -1;
-    PyObject *iterator, *item;
-    long signum;
-
-    sigemptyset(mask);
-
-    iterator = PyObject_GetIter(iterable);
-    if (iterator == NULL)
-        goto error;
-
-    while (1)
-    {
-        item = PyIter_Next(iterator);
-        if (item == NULL) {
-            if (PyErr_Occurred())
-                goto error;
-            else
-                break;
-        }
-
-        signum = PyLong_AsLong(item);
-        Py_DECREF(item);
-        if (signum == -1 && PyErr_Occurred())
-            goto error;
-        if (0 < signum && signum < NSIG) {
-            if (sigaddset(mask, (int)signum)) {
-                if (errno != EINVAL) {
-                    /* Probably impossible */
-                    PyErr_SetFromErrno(PyExc_OSError);
-                    goto error;
-                }
-                /* For backwards compatibility, allow idioms such as
-                 * `range(1, NSIG)` but warn about invalid signal numbers
-                 */
-                const char *msg =
-                    "invalid signal number %ld, please use valid_signals()";
-                if (PyErr_WarnFormat(PyExc_RuntimeWarning, 1, msg, signum)) {
-                    goto error;
-                }
-            }
-        }
-        else {
-            PyErr_Format(PyExc_ValueError,
-                         "signal number %ld out of range", signum);
-            goto error;
-        }
-    }
-    result = 0;
-
-error:
-    Py_XDECREF(iterator);
-    return result;
-}
-#endif
-
 #if defined(PYPTHREAD_SIGMASK) || defined(HAVE_SIGPENDING)
 static PyObject*
 sigset_to_set(sigset_t mask)
@@ -913,23 +858,20 @@
 signal.pthread_sigmask
 
     how:  int
-    mask: object
+    mask: sigset_t
     /
 
 Fetch and/or change the signal mask of the calling thread.
 [clinic start generated code]*/
 
 static PyObject *
-signal_pthread_sigmask_impl(PyObject *module, int how, PyObject *mask)
-/*[clinic end generated code: output=ff640fe092bc9181 input=f3b7d7a61b7b8283]*/
+signal_pthread_sigmask_impl(PyObject *module, int how, sigset_t mask)
+/*[clinic end generated code: output=0562c0fb192981a8 input=85bcebda442fa77f]*/
 {
-    sigset_t newmask, previous;
+    sigset_t previous;
     int err;
 
-    if (iterable_to_sigset(mask, &newmask))
-        return NULL;
-
-    err = pthread_sigmask(how, &newmask, &previous);
+    err = pthread_sigmask(how, &mask, &previous);
     if (err != 0) {
         errno = err;
         PyErr_SetFromErrno(PyExc_OSError);
@@ -977,7 +919,7 @@
 /*[clinic input]
 signal.sigwait
 
-    sigset: object
+    sigset: sigset_t
     /
 
 Wait for a signal.
@@ -988,17 +930,13 @@
 [clinic start generated code]*/
 
 static PyObject *
-signal_sigwait(PyObject *module, PyObject *sigset)
-/*[clinic end generated code: output=557173647424f6e4 input=11af2d82d83c2e94]*/
+signal_sigwait_impl(PyObject *module, sigset_t sigset)
+/*[clinic end generated code: output=f43770699d682f96 input=a6fbd47b1086d119]*/
 {
-    sigset_t set;
     int err, signum;
 
-    if (iterable_to_sigset(sigset, &set))
-        return NULL;
-
     Py_BEGIN_ALLOW_THREADS
-    err = sigwait(&set, &signum);
+    err = sigwait(&sigset, &signum);
     Py_END_ALLOW_THREADS
     if (err) {
         errno = err;
@@ -1113,7 +1051,7 @@
 /*[clinic input]
 signal.sigwaitinfo
 
-    sigset: object
+    sigset: sigset_t
     /
 
 Wait synchronously until one of the signals in *sigset* is delivered.
@@ -1122,20 +1060,16 @@
 [clinic start generated code]*/
 
 static PyObject *
-signal_sigwaitinfo(PyObject *module, PyObject *sigset)
-/*[clinic end generated code: output=c40f27b269cd2309 input=f3779a74a991e171]*/
+signal_sigwaitinfo_impl(PyObject *module, sigset_t sigset)
+/*[clinic end generated code: output=1eb2f1fa236fdbca input=3d1a7e1f27fc664c]*/
 {
-    sigset_t set;
     siginfo_t si;
     int err;
     int async_err = 0;
 
-    if (iterable_to_sigset(sigset, &set))
-        return NULL;
-
     do {
         Py_BEGIN_ALLOW_THREADS
-        err = sigwaitinfo(&set, &si);
+        err = sigwaitinfo(&sigset, &si);
         Py_END_ALLOW_THREADS
     } while (err == -1
              && errno == EINTR && !(async_err = PyErr_CheckSignals()));
@@ -1152,7 +1086,7 @@
 /*[clinic input]
 signal.sigtimedwait
 
-    sigset:  object
+    sigset: sigset_t
     timeout as timeout_obj: object
     /
 
@@ -1162,12 +1096,11 @@
 [clinic start generated code]*/
 
 static PyObject *
-signal_sigtimedwait_impl(PyObject *module, PyObject *sigset,
+signal_sigtimedwait_impl(PyObject *module, sigset_t sigset,
                          PyObject *timeout_obj)
-/*[clinic end generated code: output=f7eff31e679f4312 input=53fd4ea3e3724eb8]*/
+/*[clinic end generated code: output=59c8971e8ae18a64 input=87fd39237cf0b7ba]*/
 {
     struct timespec ts;
-    sigset_t set;
     siginfo_t si;
     int res;
     _PyTime_t timeout, deadline, monotonic;
@@ -1181,9 +1114,6 @@
         return NULL;
     }
 
-    if (iterable_to_sigset(sigset, &set))
-        return NULL;
-
     deadline = _PyTime_GetMonotonicClock() + timeout;
 
     do {
@@ -1191,7 +1121,7 @@
             return NULL;
 
         Py_BEGIN_ALLOW_THREADS
-        res = sigtimedwait(&set, &si, &ts);
+        res = sigtimedwait(&sigset, &si, &ts);
         Py_END_ALLOW_THREADS
 
         if (res != -1)