diff --git a/setup.py b/setup.py
index d29d7b9..ef7b5b1 100755
--- a/setup.py
+++ b/setup.py
@@ -113,6 +113,7 @@ setup(
         'pyyaml',
         'argparse',
         'argcomplete',
+        'future'
     ],
     setup_requires=[
         'setuptools_scm',
diff --git a/src/escpos/magicencode.py b/src/escpos/magicencode.py
index ded60b8..770703c 100644
--- a/src/escpos/magicencode.py
+++ b/src/escpos/magicencode.py
@@ -145,7 +145,7 @@ class Encoder(object):
         :param encoding: Encoding name to use (must be defined in capabilities)
         :param defaultchar: Fallback for non-encodable characters
         """
-        codepage_char_map = self.available_characters[encoding]
+        codepage_char_map = self._get_codepage_char_map(encoding)
         output_bytes = bytes([self._encode_char(char, codepage_char_map, defaultchar) for char in text])
         return output_bytes
 
diff --git a/test/test_function_text.py b/test/test_function_text.py
index d4de426..7f3869c 100644
--- a/test/test_function_text.py
+++ b/test/test_function_text.py
@@ -20,7 +20,7 @@ from escpos.printer import Dummy
 
 
 def get_printer():
-    return Dummy(magic_encode_args={'disabled': True, 'encoding': 'cp437'})
+    return Dummy(magic_encode_args={'disabled': True, 'encoding': 'CP437'})
 
 
 @given(text=st.text())
diff --git a/test/test_magicencode.py b/test/test_magicencode.py
index 665369e..45b0d55 100644
--- a/test/test_magicencode.py
+++ b/test/test_magicencode.py
@@ -26,13 +26,13 @@ from escpos.exceptions import CharCodeError, Error
 class TestEncoder:
 
     def test_can_encode(self):
-        assert not Encoder({'cp437': 1}).can_encode('cp437', u'€')
-        assert Encoder({'cp437': 1}).can_encode('cp437', u'á')
+        assert not Encoder({'CP437': 1}).can_encode('CP437', u'€')
+        assert Encoder({'CP437': 1}).can_encode('CP437', u'á')
         assert not Encoder({'foobar': 1}).can_encode('foobar', 'a')
 
     def test_find_suitable_encoding(self):
-        assert not Encoder({'cp437': 1}).find_suitable_encoding(u'€')
-        assert Encoder({'cp858': 1}).find_suitable_encoding(u'€') == 'cp858'
+        assert not Encoder({'CP437': 1}).find_suitable_encoding(u'€')
+        assert Encoder({'CP858': 1}).find_suitable_encoding(u'€') == 'CP858'
 
     @raises(ValueError)
     def test_get_encoding(self):
@@ -51,17 +51,17 @@ class TestMagicEncode:
 
         def test_init_from_none(self, driver):
             encode = MagicEncode(driver, encoding=None)
-            encode.write_with_encoding('cp858', '€ ist teuro.')
+            encode.write_with_encoding('CP858', '€ ist teuro.')
             assert driver.output == b'\x1bt\x13\xd5 ist teuro.'
 
         def test_change_from_another(self, driver):
-            encode = MagicEncode(driver, encoding='cp437')
-            encode.write_with_encoding('cp858', '€ ist teuro.')
+            encode = MagicEncode(driver, encoding='CP437')
+            encode.write_with_encoding('CP858', '€ ist teuro.')
             assert driver.output == b'\x1bt\x13\xd5 ist teuro.'
 
         def test_no_change(self, driver):
-            encode = MagicEncode(driver, encoding='cp858')
-            encode.write_with_encoding('cp858', '€ ist teuro.')
+            encode = MagicEncode(driver, encoding='CP858')
+            encode.write_with_encoding('CP858', '€ ist teuro.')
             assert driver.output == b'\xd5 ist teuro.'
 
     class TestWrite:
@@ -72,14 +72,14 @@ class TestMagicEncode:
             assert driver.output == b'\x1bt\x0f\xa4 ist teuro.'
 
         def test_write_disabled(self, driver):
-            encode = MagicEncode(driver, encoding='cp437', disabled=True)
+            encode = MagicEncode(driver, encoding='CP437', disabled=True)
             encode.write('€ ist teuro.')
             assert driver.output == b'? ist teuro.'
 
         def test_write_no_codepage(self, driver):
             encode = MagicEncode(
-                driver, defaultsymbol="_", encoder=Encoder({'cp437': 1}),
-                encoding='cp437')
+                driver, defaultsymbol="_", encoder=Encoder({'CP437': 1}),
+                encoding='CP437')
             encode.write(u'€ ist teuro.')
             assert driver.output == b'_ ist teuro.'
 
@@ -87,7 +87,7 @@ class TestMagicEncode:
 
         def test(self, driver):
             encode = MagicEncode(driver)
-            encode.force_encoding('cp437')
+            encode.force_encoding('CP437')
             assert driver.output == b'\x1bt\x00'
 
             encode.write('€ ist teuro.')