diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
index 600d476..c5e48df 100644
--- a/Lib/test/test_time.py
+++ b/Lib/test/test_time.py
@@ -122,6 +122,9 @@
     def test_asctime(self):
         time.asctime(time.gmtime(self.t))
         self.assertRaises(TypeError, time.asctime, 0)
+        self.assertRaises(TypeError, time.asctime, ())
+        self.assertRaises(ValueError, time.asctime,
+                          (12345, 1, 0, 0, 0, 0, 0, 0, 0))
 
     def test_asctime_bounding_check(self):
         self._bounds_checking(time.asctime)
diff --git a/Modules/timemodule.c b/Modules/timemodule.c
index 89666a4..e8ea661 100644
--- a/Modules/timemodule.c
+++ b/Modules/timemodule.c
@@ -620,6 +620,10 @@
     } else if (!gettmarg(tup, &buf) || !checktm(&buf))
         return NULL;
     p = asctime(&buf);
+    if (p == NULL) {
+        PyErr_SetString(PyExc_ValueError, "invalid time");
+        return NULL;
+    }
     if (p[24] == '\n')
         p[24] = '\0';
     return PyUnicode_FromString(p);