diff --git a/pymath/expression.py b/pymath/expression.py
index 99f0761..1e63c53 100644
--- a/pymath/expression.py
+++ b/pymath/expression.py
@@ -150,6 +150,9 @@ class Expression(object):
                     tokens.append("*")
                 tokens.append(character)
 
+            elif character == ".":
+                raise ValueError("No float number please")
+
             elif character != " ":
                 raise ValueError("{} is an unvalid character".format(character))
 
diff --git a/test/test_expression.py b/test/test_expression.py
index 16276ba..d079e77 100644
--- a/test/test_expression.py
+++ b/test/test_expression.py
@@ -48,6 +48,10 @@ class TestExpression(unittest.TestCase):
         tok = Expression.str2tokens(exp)
         self.assertEqual(tok, [-3, "*","(", 2, ")" ])
 
+    def test_str2tokens_error_float(self):
+        exp = "1 + 1.3"
+        self.assertRaises(ValueError, Expression.str2tokens, exp)
+
     def test_str2tokens_error(self):
         exp = "1 + $"
         self.assertRaises(ValueError, Expression.str2tokens, exp)