diff --git a/escpos/constants.py b/escpos/constants.py
index ca6efb7..9315395 100644
--- a/escpos/constants.py
+++ b/escpos/constants.py
@@ -132,29 +132,29 @@ BARCODE_WIDTH  = GS + 'w'  # Barcode Width  [2-6]
 _SET_BARCODE_TYPE = lambda m: GS + 'k' + m
 
 # Barcodes for type A
-BARCODE_A_UPC_A  = _SET_BARCODE_TYPE('\x00')  # Barcode type UPC-A
-BARCODE_A_UPC_E  = _SET_BARCODE_TYPE('\x01')  # Barcode type UPC-E
-BARCODE_A_EAN13  = _SET_BARCODE_TYPE('\x02')  # Barcode type EAN13
-BARCODE_A_EAN8   = _SET_BARCODE_TYPE('\x03')  # Barcode type EAN8
-BARCODE_A_CODE39 = _SET_BARCODE_TYPE('\x04')  # Barcode type CODE39
-BARCODE_A_ITF    = _SET_BARCODE_TYPE('\x05')  # Barcode type ITF
-BARCODE_A_NW7    = _SET_BARCODE_TYPE('\x06')  # Barcode type NW7
+BARCODE_A_UPC_A  = _SET_BARCODE_TYPE(chr(0))  # Barcode type UPC-A
+BARCODE_A_UPC_E  = _SET_BARCODE_TYPE(chr(1))  # Barcode type UPC-E
+BARCODE_A_EAN13  = _SET_BARCODE_TYPE(chr(2))  # Barcode type EAN13
+BARCODE_A_EAN8   = _SET_BARCODE_TYPE(chr(3))  # Barcode type EAN8
+BARCODE_A_CODE39 = _SET_BARCODE_TYPE(chr(4))  # Barcode type CODE39
+BARCODE_A_ITF    = _SET_BARCODE_TYPE(chr(5))  # Barcode type ITF
+BARCODE_A_NW7    = _SET_BARCODE_TYPE(chr(6))  # Barcode type NW7
 
 # Barcodes for type B
-BARCODE_B_UPC_A  = _SET_BARCODE_TYPE('\x65')  # Barcode type UPC-A
-BARCODE_B_UPC_E  = _SET_BARCODE_TYPE('\x66')  # Barcode type UPC-E
-BARCODE_B_EAN13  = _SET_BARCODE_TYPE('\x67')  # Barcode type EAN13
-BARCODE_B_EAN8   = _SET_BARCODE_TYPE('\x68')  # Barcode type EAN8
-BARCODE_B_CODE39 = _SET_BARCODE_TYPE('\x69')  # Barcode type CODE39
-BARCODE_B_ITF    = _SET_BARCODE_TYPE('\x70')  # Barcode type ITF
-BARCODE_B_NW7    = _SET_BARCODE_TYPE('\x71')  # Barcode type NW7
-BARCODE_B_CODE93 = _SET_BARCODE_TYPE('\x72')  # Barcode type CODE93
-BARCODE_B_CODE128 = _SET_BARCODE_TYPE('\x73')  # Barcode type CODE128
-BARCODE_B_GS1_128 = _SET_BARCODE_TYPE('\x74')  # Barcode type GS1_128
-BARCODE_B_GS1_DATABAR_OMNI = _SET_BARCODE_TYPE('\x75')  # Barcode type GS1 DataBar Omnidirectional
-BARCODE_B_GS1_DATABAR_TRUNC = _SET_BARCODE_TYPE('\x76')  # Barcode type GS1 DataBar Truncated
-BARCODE_B_GS1_DATABAR_LIM = _SET_BARCODE_TYPE('\x77')  # Barcode type GS1 DataBar Limited
-BARCODE_B_GS1_DATABAR_EXP = _SET_BARCODE_TYPE('\x78')  # Barcode type GS1 DataBar Expanded
+BARCODE_B_UPC_A             = _SET_BARCODE_TYPE(chr(65))  # Barcode type UPC-A
+BARCODE_B_UPC_E             = _SET_BARCODE_TYPE(chr(66))  # Barcode type UPC-E
+BARCODE_B_EAN13             = _SET_BARCODE_TYPE(chr(67))  # Barcode type EAN13
+BARCODE_B_EAN8              = _SET_BARCODE_TYPE(chr(68))  # Barcode type EAN8
+BARCODE_B_CODE39            = _SET_BARCODE_TYPE(chr(69))  # Barcode type CODE39
+BARCODE_B_ITF               = _SET_BARCODE_TYPE(chr(70))  # Barcode type ITF
+BARCODE_B_NW7               = _SET_BARCODE_TYPE(chr(71))  # Barcode type NW7
+BARCODE_B_CODE93            = _SET_BARCODE_TYPE(chr(72))  # Barcode type CODE93
+BARCODE_B_CODE128           = _SET_BARCODE_TYPE(chr(73))  # Barcode type CODE128
+BARCODE_B_GS1_128           = _SET_BARCODE_TYPE(chr(74))  # Barcode type GS1_128
+BARCODE_B_GS1_DATABAR_OMNI  = _SET_BARCODE_TYPE(chr(75))  # Barcode type GS1 DataBar Omnidirectional
+BARCODE_B_GS1_DATABAR_TRUNC = _SET_BARCODE_TYPE(chr(76))  # Barcode type GS1 DataBar Truncated
+BARCODE_B_GS1_DATABAR_LIM   = _SET_BARCODE_TYPE(chr(77))  # Barcode type GS1 DataBar Limited
+BARCODE_B_GS1_DATABAR_EXP   = _SET_BARCODE_TYPE(chr(78))  # Barcode type GS1 DataBar Expanded
 
 # Constants to be used when the user is calling the function. All uppercase.
 BARCODE_TYPE_A = {