diff --git a/Lib/test/test_curses.py b/Lib/test/test_curses.py
index 897d738f57d..6bbb3fc97c4 100644
--- a/Lib/test/test_curses.py
+++ b/Lib/test/test_curses.py
@@ -188,6 +188,9 @@ class TestCurses(unittest.TestCase):
         if hasattr(curses, 'enclose'):
             stdscr.enclose()
 
+        self.assertRaises(ValueError, stdscr.getstr, -400)
+        self.assertRaises(ValueError, stdscr.getstr, 2, 3, -400)
+
 
     def test_module_funcs(self):
         "Test module-level functions"
diff --git a/Misc/NEWS b/Misc/NEWS
index ed580d1c003..60d6c5f41bb 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -37,6 +37,9 @@ Library
 - Issue #26750: unittest.mock.create_autospec() now works properly for
   subclasses of property() and other data descriptors.
 
+- In the curses module, raise an error if window.getstr() is passed a negative
+  value.
+
 - Issue #27758: Fix possible integer overflow in the _csv module for large record
   lengths.
 
diff --git a/Modules/_cursesmodule.c b/Modules/_cursesmodule.c
index d64bdc74e91..06aa46c3130 100644
--- a/Modules/_cursesmodule.c
+++ b/Modules/_cursesmodule.c
@@ -1221,6 +1221,10 @@ PyCursesWindow_GetStr(PyCursesWindowObject *self, PyObject *args)
     case 1:
         if (!PyArg_ParseTuple(args,"i;n", &n))
             return NULL;
+        if (n < 0) {
+            PyErr_SetString(PyExc_ValueError, "'n' must be nonnegative");
+            return NULL;
+        }
         Py_BEGIN_ALLOW_THREADS
         rtn2 = wgetnstr(self->win, rtn, Py_MIN(n, 1023));
         Py_END_ALLOW_THREADS
@@ -1239,6 +1243,10 @@ PyCursesWindow_GetStr(PyCursesWindowObject *self, PyObject *args)
     case 3:
         if (!PyArg_ParseTuple(args,"iii;y,x,n", &y, &x, &n))
             return NULL;
+        if (n < 0) {
+            PyErr_SetString(PyExc_ValueError, "'n' must be nonnegative");
+            return NULL;
+        }
 #ifdef STRICT_SYSV_CURSES
         Py_BEGIN_ALLOW_THREADS
         rtn2 = wmove(self->win,y,x)==ERR ? ERR :