diff --git a/tablib/core.py b/tablib/core.py
index bd2d4ba..c3013ed 100644
--- a/tablib/core.py
+++ b/tablib/core.py
@@ -615,10 +615,14 @@ class Databook(object):
 	"""A book of :class:`Dataset` objects.
 	"""
 
-	def __init__(self, sets=[]):
-		self._datasets = sets
-		self._register_formats()
+	def __init__(self, sets=None):
 
+		if sets is None:
+			self._datasets = list()
+		else:
+			self._datasets = sets
+
+		self._register_formats()
 
 	def __repr__(self):
 		try: