diff --git a/.travis.yml b/.travis.yml
index 21ba88d..0da8c1d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,16 @@
 language: python
 sudo: false
 cache: pip
+matrix:
+  include:
+  - python: 2.7
+    env: TOXENV=py27
+  - python: 3.4
+    env: TOXENV=py34
+  - python: 3.5
+    env: TOXENV=py35
 before_install:
     - pip install tox
 # command to run tests
 script:
-    - tox
\ No newline at end of file
+    - tox
diff --git a/escpos/escpos.py b/escpos/escpos.py
index a5bac17..467cf4d 100644
--- a/escpos/escpos.py
+++ b/escpos/escpos.py
@@ -83,7 +83,7 @@ class Escpos(object):
         pbuffer = b''
 
         self._raw(S_RASTER_N)
-        pbuffer = "%02X%02X%02X%02X" % (((size[0]/size[1])/8), 0, size[1] & 0xff, size[1] >> 8)
+        pbuffer = "%02X%02X%02X%02X" % (((size[0]//size[1])//8), 0, size[1] & 0xff, size[1] >> 8)
         self._raw(binascii.unhexlify(pbuffer))
         pbuffer = ""
 
diff --git a/tox.ini b/tox.ini
index 0a56f96..c7460c5 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py27, py34
+envlist = py27, py34, py35
 
 [testenv]
 deps = nose