diff --git a/escpos/constants.py b/escpos/constants.py
index 9315395..dcac0d3 100644
--- a/escpos/constants.py
+++ b/escpos/constants.py
@@ -150,7 +150,7 @@ 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_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
@@ -179,7 +179,7 @@ BARCODE_TYPE_B = {
     'CODABAR': BARCODE_B_NW7,
     'CODE93': BARCODE_B_CODE93,
     'CODE128': BARCODE_B_CODE128,
-    'GS1_128': BARCODE_B_GS1_128,
+    'GS1-128': BARCODE_B_GS1_128,
     'GS1 DATABAR OMNIDIRECTIONAL': BARCODE_B_GS1_DATABAR_OMNI,
     'GS1 DATABAR TRUNCATED': BARCODE_B_GS1_DATABAR_TRUNC,
     'GS1 DATABAR LIMITED': BARCODE_B_GS1_DATABAR_LIM,