diff --git a/barcode/__init__.py b/barcode/__init__.py
index d0d15cd..dd8ad1e 100755
--- a/barcode/__init__.py
+++ b/barcode/__init__.py
@@ -1,5 +1,5 @@
-"""This package provides a simple way to create standard barcodes.
-It needs no external packages to be installed, the barcodes are
+"""This package provides a simple way to create standard barcodes.  It needs no
+external packages to be installed (exception: 'luhn' for MSI), the barcodes are
 created as SVG objects. If Pillow is installed, the barcodes can also be
 rendered as images (all formats supported by Pillow).
 """
@@ -9,6 +9,7 @@
 from typing import Union
 
 from barcode.codabar import CODABAR
+from barcode.codex import MSI
 from barcode.codex import PZN
 from barcode.codex import Code39
 from barcode.codex import Code128
@@ -50,6 +51,7 @@
     "gs1_128": Gs1_128,
     "codabar": CODABAR,
     "nw-7": CODABAR,
+    "msi": MSI,
 }
 
 PROVIDED_BARCODES = list(__BARCODE_MAP)
diff --git a/barcode/codex.py b/barcode/codex.py
index 74665be..6482887 100755
--- a/barcode/codex.py
+++ b/barcode/codex.py
@@ -1,6 +1,6 @@
 """Module: barcode.codex
 
-:Provided barcodes: Code 39, Code 128, PZN
+:Provided barcodes: Code 39, Code 128, PZN, MSI
 """
 from barcode.base import Barcode
 from barcode.charsets import code39
@@ -77,11 +77,10 @@ def render(self, writer_options=None, text=None):
 class PZN7(Code39):
     """Initializes new German number for pharmaceutical products.
 
-    :parameters:
-        pzn : String
-            Code to render.
-        writer : barcode.writer Instance
-            The writer to render the barcode (default: SVGWriter).
+    :param pzn: String
+        Code to render.
+    :param writer: barcode.writer Instance
+        The writer to render the barcode (default: SVGWriter).
     """
 
     name = "Pharmazentralnummer"
@@ -122,10 +121,9 @@ class Code128(Barcode):
     """Initializes a new Code128 instance. The checksum is added automatically
     when building the bars.
 
-    :parameters:
-        code : String
+        :param code: String
             Code 128 string without checksum (added automatically).
-        writer : barcode.writer Instance
+        :param writer: barcode.writer Instance
             The writer to render the barcode (default: SVGWriter).
     """
 
@@ -271,5 +269,78 @@ def get_fullcode(self):
         return super().get_fullcode()[1:]
 
 
+class MSI(Barcode):
+    """Initializes a new MSI (Modified Plessey) instance. The checksum is added
+    automatically when building the bars.
+
+    :parameters:
+        :param code: int or bytes
+            Code MSI int without checksum (added automatically).
+            Code bytes without checksum. requires byteorder (WARNING: non-standard use)
+        :param writer: barcode.writer Instance
+            The writer to render the barcode (default: SVGWriter).
+        :param byteorder: string
+            'big' or 'little' ; to convert bytes to int
+        :param encoding: string
+            if set, convert bytes to string and use this as a label. defaults to utf-8
+            if unset, use integer value as label
+            Note: for convenience ; label can also be set when calling save() with param
+            'text'
+
+    limitations:
+        - only one check digit (Luhn Mod10)
+        - only standard prefix/suffix
+
+    """
+
+    name = "MSI/Modified Plessey"
+
+    def __init__(
+        self,
+        code,
+        writer=None,
+        byteorder=None,
+        encoding="utf-8",
+    ):
+        self.writer = writer or self.default_writer()
+        self._buffer = ""
+
+        if type(code) is int:
+            self.label = self.code = str(code)
+        elif type(code) is bytes:
+            self.code = str(int.from_bytes(code, byteorder))
+            if encoding is not None:
+                self.label = code.decode(encoding)
+            else:
+                self.label = self.code if label is None else label
+
+    def __str__(self):
+        return self.label
+
+    @property
+    def encoded(self):
+        return self._build()
+
+    def get_fullcode(self):
+        return self.label
+
+    def _build(self):
+        """
+        check digit is computed with https://pypi.org/project/luhn/
+        """
+        from luhn import append as luhn_check_append
+
+        bcd = "".join([f"{bin(int(n))[2:]:0>4}" for n in luhn_check_append(self.code)])
+
+        conv = {
+            "0": "100",
+            "1": "110",
+        }
+        return ["110" + "".join([conv[i] for i in bcd]) + "1001"]
+
+    def build(self):
+        return self.encoded
+
+
 # For pre 0.8 compatibility
 PZN = PZN7
diff --git a/barcode/writer.py b/barcode/writer.py
index 3a3dcd0..90247fc 100755
--- a/barcode/writer.py
+++ b/barcode/writer.py
@@ -322,14 +322,15 @@ def _init(self, code):
         attributes = {"id": "barcode_group"}
         _set_attributes(group, **attributes)
         self._group = self._root.appendChild(group)
-        background = self._document.createElement("rect")
-        attributes = {
-            "width": "100%",
-            "height": "100%",
-            "style": f"fill:{self.background}",
-        }
-        _set_attributes(background, **attributes)
-        self._group.appendChild(background)
+        if self.background:
+            background = self._document.createElement("rect")
+            attributes = {
+                "width": "100%",
+                "height": "100%",
+                "style": f"fill:{self.background}",
+            }
+            _set_attributes(background, **attributes)
+            self._group.appendChild(background)
 
     def _create_module(self, xpos, ypos, width, color):
         # Background rect has been provided already, so skipping "spaces"