diff -r fd9c9579050d Lib/test/test_parser.py
--- a/Lib/test/test_parser.py	Sun Nov 25 13:25:57 2012 +0000
+++ b/Lib/test/test_parser.py	Sun Nov 25 16:00:28 2012 +0000
@@ -567,6 +567,17 @@
         st = parser.suite('a = u"\u1"')
         self.assertRaises(SyntaxError, parser.compilest, st)
 
+    def test_issue_9011(self):
+        # Issue 9011: compilation of an unary minus expression changed
+        # the meaning of the ST, so that a second compilation produced
+        # incorrect results.
+        st = parser.expr('-3')
+        code1 = parser.compilest(st)
+        self.assertEqual(eval(code1), -3)
+        code2 = parser.compilest(st)
+        self.assertEqual(eval(code2), -3)
+
+
 class ParserStackLimitTestCase(unittest.TestCase):
     """try to push the parser to/over it's limits.
     see http://bugs.python.org/issue1881 for a discussion
diff -r fd9c9579050d Python/ast.c
--- a/Python/ast.c	Sun Nov 25 13:25:57 2012 +0000
+++ b/Python/ast.c	Sun Nov 25 16:00:28 2012 +0000
@@ -1744,14 +1744,19 @@
         NCH(ppower) == 1 &&
         TYPE((patom = CHILD(ppower, 0))) == atom &&
         TYPE((pnum = CHILD(patom, 0))) == NUMBER) {
+        PyObject *pynum;
         char *s = PyObject_MALLOC(strlen(STR(pnum)) + 2);
         if (s == NULL)
             return NULL;
         s[0] = '-';
         strcpy(s + 1, STR(pnum));
-        PyObject_FREE(STR(pnum));
-        STR(pnum) = s;
-        return ast_for_atom(c, patom);
+        pynum = parsenumber(c, s);
+        PyObject_FREE(s);
+        if (!pynum)
+            return NULL;
+
+        PyArena_AddPyObject(c->c_arena, pynum);
+        return Num(pynum, LINENO(n), n->n_col_offset, c->c_arena);
     }
 
     expression = ast_for_expr(c, CHILD(n, 1));