diff --git a/X3GWriter.py b/X3GWriter.py
index 020355a..cac60c9 100644
--- a/X3GWriter.py
+++ b/X3GWriter.py
@@ -27,7 +27,7 @@ class X3GWriter(MeshWriter):
 	\param mode The output mode to use. This is ignored, since it has no
 	meaning. X3G is always a binary file.
 	"""
-	def write(self, stream, nodes, mode = MeshWriter.OutputMode.TextMode):
+	def write(self, stream, nodes, mode = MeshWriter.OutputMode.TextMode, mime_type=None):
 		# Write the g-code to a temporary file.
 		temp_gcode = None
 		try: