diff --git a/pymath/polynom.py b/pymath/polynom.py
index 646bfcf..657f288 100644
--- a/pymath/polynom.py
+++ b/pymath/polynom.py
@@ -137,36 +137,52 @@ class Polynom(object):
         """
         postfix = []
         for (i,a) in list(enumerate(self._coef))[::-1]:
-            operator = op.add
+            operator = [op.add]
+            operator_sub1 = []
             if type(a) == Expression:
                 # case coef is an arithmetic expression
                 c = self.coef_postfix(a.postfix_tokens,i)
                 if c != []:
                     postfix.append(c)
                     if len(postfix) > 1:
-                        postfix.append(operator)
+                        postfix += operator
 
             elif type(a) == list:
                 # case need to repeat the x^i
                 for b in a:
-                    if len(postfix) > 0 and isNumber(b) and b < 0:
-                        b = -b
-                        operator = op.sub
-                    c = self.coef_postfix([b],i)
+                    if len(postfix) == 0 and isNumber(b) and b < 0:
+                        b = [-b]
+                        operator_sub1 = [op.sub1]
+                    elif len(postfix) > 0 and isNumber(b) and b < 0:
+                        b = [-b]
+                        operator = [op.sub]
+                    else:
+                        b = [b]
+                    c = self.coef_postfix(b,i)
                     if c != []:
                         postfix.append(c)
                         if len(postfix) > 1:
-                            postfix.append(operator)
+                            postfix += operator_sub1
+                            postfix += operator
+                        postfix += operator_sub1
 
             elif a != 0:
-                if len(postfix) > 0 and a < 0:
-                    a = -a
-                    operator = op.sub
-                c = self.coef_postfix([a],i)
+                if len(postfix) == 0 and a < 0:
+                        a = [-a]
+                        operator_sub1 = [op.sub1]
+                elif len(postfix) > 0 and a < 0:
+                    a = [-a]
+                    operator = [op.sub]
+                else:
+                    a = [a]
+
+                c = self.coef_postfix(a,i)
                 if c != []:
                     postfix.append(c)
                     if len(postfix) > 1:
-                        postfix.append(operator)
+                        postfix += operator_sub1
+                        postfix += operator
+                    postfix += operator_sub1
 
         return flatten_list(postfix)
 
diff --git a/test/test_polynom.py b/test/test_polynom.py
index 96e9970..4a80e80 100644
--- a/test/test_polynom.py
+++ b/test/test_polynom.py
@@ -77,7 +77,7 @@ class TestPolynom(unittest.TestCase):
         # TODO: Choix arbitraire (vis à vis des + et des -) il faudra faire en fonction de render |sam. juin 14 09:45:55 CEST 2014
         p = Polynom([-1,-2,-3])
         #ans = [-1, -2, "x", "*", "+", -3, "x", 2, "^", "*", "+"]
-        ans = [-3, 'x', 2, '^', '*', 2, 'x', '*', '-', 1, '-']
+        ans = [3, 'x', 2, '^', '*', '-', 2, 'x', '*', '-', 1, '-']
         self.assertEqual(ans, p.postfix)
 
     def test_postfix_multi_coef(self):
@@ -118,6 +118,25 @@ class TestPolynom(unittest.TestCase):
         r = (p + q)[-1]
         self.assertEqual(str(r), '6 x ^ 2 + 2 x + 1')
 
+    def test_sub_int(self):
+        p = Polynom([1, 2, 3])
+        q = (p - 2)[-1]
+        self.assertEqual(str(q), '3 x ^ 2 + 2 x - 1')
+
+    def test_sub_frac(self):
+        p = Polynom([1, 2, 3])
+        f = Fraction(1, 2)
+        q = (p - f)[-1]
+        #ans = repr(Polynom([Expression(Fraction(3, 2)), Expression(2), Expression(3)]))
+        self.assertEqual(str(q),'3 x ^ 2 + 2 x + 1 / 2')
+
+    def test_sub_poly(self):
+        p = Polynom([1, 0, 2])
+        q = Polynom([0, 2, 3])
+        r = (p - q)[-1]
+        self.assertEqual(str(r), '- x ^ 2 - 2 x + 1')
+
+
     def test_radd_int(self):
         pass