diff --git a/Doc/c-api/time.rst b/Doc/c-api/time.rst
index 17ddbc5f9cd3e75..5cfdef71b3e191e 100644
--- a/Doc/c-api/time.rst
+++ b/Doc/c-api/time.rst
@@ -78,8 +78,12 @@ Raw Clock Functions
 Similar to clock functions, but don't set an exception on error and don't
 require the caller to hold the GIL.
 
-The functions return ``0`` on success, or set ``*result`` to ``0`` return
-``-1`` on failure.
+On success, the functions return ``0``.
+
+On failure, they set ``*result`` to ``0`` and return ``-1``, *without* setting
+an exception. To get the cause of the error, acquire the GIL and call the
+regular (non-``Raw``) function. Note that the regular function may succeed after
+the ``Raw`` one failed.
 
 .. c:function:: int PyTime_MonotonicRaw(PyTime_t *result)
 
diff --git a/Modules/_testcapi/time.c b/Modules/_testcapi/time.c
index 3f07c1c48360714..464cf5c3125012e 100644
--- a/Modules/_testcapi/time.c
+++ b/Modules/_testcapi/time.c
@@ -51,6 +51,7 @@ test_pytime_monotonic(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args))
     PyTime_t t;
     int res = PyTime_Monotonic(&t);
     if (res < 0) {
+        assert(t == 0);
         return NULL;
     }
     assert(res == 0);
@@ -67,6 +68,7 @@ test_pytime_monotonic_raw(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args))
     res = PyTime_MonotonicRaw(&t);
     Py_END_ALLOW_THREADS
     if (res < 0) {
+        assert(t == 0);
         PyErr_SetString(PyExc_RuntimeError, "PyTime_MonotonicRaw() failed");
         return NULL;
     }
@@ -81,6 +83,7 @@ test_pytime_perf_counter(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args))
     PyTime_t t;
     int res = PyTime_PerfCounter(&t);
     if (res < 0) {
+        assert(t == 0);
         return NULL;
     }
     assert(res == 0);
@@ -97,6 +100,7 @@ test_pytime_perf_counter_raw(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args
     res = PyTime_PerfCounterRaw(&t);
     Py_END_ALLOW_THREADS
     if (res < 0) {
+        assert(t == 0);
         PyErr_SetString(PyExc_RuntimeError, "PyTime_PerfCounterRaw() failed");
         return NULL;
     }
@@ -111,6 +115,7 @@ test_pytime_time(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args))
     PyTime_t t;
     int res = PyTime_Time(&t);
     if (res < 0) {
+        assert(t == 0);
         return NULL;
     }
     assert(res == 0);
@@ -127,6 +132,7 @@ test_pytime_time_raw(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args))
     res = PyTime_TimeRaw(&t);
     Py_END_ALLOW_THREADS
     if (res < 0) {
+        assert(t == 0);
         PyErr_SetString(PyExc_RuntimeError, "PyTime_TimeRaw() failed");
         return NULL;
     }
diff --git a/Python/pytime.c b/Python/pytime.c
index d8c46af99b979a5..d2bda090ad99d36 100644
--- a/Python/pytime.c
+++ b/Python/pytime.c
@@ -1034,7 +1034,10 @@ PyTime_t
 _PyTime_TimeUnchecked(void)
 {
     PyTime_t t;
-    (void)PyTime_TimeRaw(&t);
+    int result = PyTime_TimeRaw(&t);
+    // We assume that getting the time succeeds on current platforms.
+    // If this ever is not the case, use PyTime_TimeRaw instead.
+    assert(result == 0);
     return t;
 }
 
@@ -1267,7 +1270,10 @@ PyTime_t
 _PyTime_MonotonicUnchecked(void)
 {
     PyTime_t t;
-    (void)PyTime_MonotonicRaw(&t);
+    int result = PyTime_MonotonicRaw(&t);
+    // We assume that getting the time succeeds on current platforms.
+    // If this ever is not the case, use PyTime_MonotonicRaw instead.
+    assert(result == 0);
     return t;
 }