diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index f7471e55b9f..a2e611fe9e0 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -624,10 +624,9 @@ class TestInvalidFD(unittest.TestCase):
         if hasattr(os, "fpathconf"):
             self.assertRaises(OSError, os.fpathconf, 10, "PC_NAME_MAX")
 
-    #this is a weird one, it raises IOError unlike the others
     def test_ftruncate(self):
         if hasattr(os, "ftruncate"):
-            self.assertRaises(IOError, os.ftruncate, 10, 0)
+            self.assertRaises(OSError, os.ftruncate, 10, 0)
 
     def test_lseek(self):
         if hasattr(os, "lseek"):
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 490999386ab..69b69787c55 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -5114,10 +5114,8 @@ posix_ftruncate(PyObject *self, PyObject *args)
 	Py_BEGIN_ALLOW_THREADS
 	res = ftruncate(fd, length);
 	Py_END_ALLOW_THREADS
-	if (res < 0) {
-		PyErr_SetFromErrno(PyExc_IOError);
-		return NULL;
-	}
+	if (res < 0)
+		return posix_error();
 	Py_INCREF(Py_None);
 	return Py_None;
 }