Index: Lib/test/test_os.py
===================================================================
--- Lib/test/test_os.py	(revision 68622)
+++ Lib/test/test_os.py	(working copy)
@@ -570,10 +570,9 @@
         if hasattr(os, "fpathconf"):
             self.assertRaises(OSError, os.fpathconf, 10, "PC_FILESIZEBITS")
 
-    #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"):
Index: Modules/posixmodule.c
===================================================================
--- Modules/posixmodule.c	(revision 68607)
+++ Modules/posixmodule.c	(working copy)
@@ -6633,7 +6633,7 @@
 	res = ftruncate(fd, length);
 	Py_END_ALLOW_THREADS
 	if (res < 0) {
-		PyErr_SetFromErrno(PyExc_IOError);
+		posix_error();
 		return NULL;
 	}
 	Py_INCREF(Py_None);