diff --git a/base/fs/partitionmaps/gpt.py b/base/fs/partitionmaps/gpt.py
index 7a95943..2d45229 100644
--- a/base/fs/partitionmaps/gpt.py
+++ b/base/fs/partitionmaps/gpt.py
@@ -8,15 +8,17 @@ class GPTPartitionMap(AbstractPartitionMap):
 
 	def __init__(self, data):
 		self.partitions = []
+
+		def last_partition():
+			return self.partitions[-1] if len(self.partitions) > 0 else None
 		if 'boot' in data:
 			self.boot = GPTPartition(data['boot']['size'], data['boot']['filesystem'], 'boot', None)
 			self.partitions.append(self.boot)
-		self.root = GPTPartition(data['root']['size'], data['root']['filesystem'], 'root',
-		                         getattr(self, 'boot', None))
-		self.partitions.append(self.root)
 		if 'swap' in data:
-			self.swap = GPTSwapPartition(data['swap']['size'], self.root)
+			self.swap = GPTSwapPartition(data['swap']['size'], last_partition())
 			self.partitions.append(self.swap)
+		self.root = GPTPartition(data['root']['size'], data['root']['filesystem'], 'root', last_partition())
+		self.partitions.append(self.root)
 
 		super(GPTPartitionMap, self).__init__()
 
diff --git a/base/fs/partitionmaps/mbr.py b/base/fs/partitionmaps/mbr.py
index 67c40cb..8b04d12 100644
--- a/base/fs/partitionmaps/mbr.py
+++ b/base/fs/partitionmaps/mbr.py
@@ -8,15 +8,17 @@ class MBRPartitionMap(AbstractPartitionMap):
 
 	def __init__(self, data):
 		self.partitions = []
+
+		def last_partition():
+			return self.partitions[-1] if len(self.partitions) > 0 else None
 		if 'boot' in data:
 			self.boot = MBRPartition(data['boot']['size'], data['boot']['filesystem'], None)
 			self.partitions.append(self.boot)
-		self.root = MBRPartition(data['root']['size'], data['root']['filesystem'],
-		                         getattr(self, 'boot', None))
-		self.partitions.append(self.root)
 		if 'swap' in data:
-			self.swap = MBRSwapPartition(data['swap']['size'], self.root)
+			self.swap = MBRSwapPartition(data['swap']['size'], last_partition())
 			self.partitions.append(self.swap)
+		self.root = MBRPartition(data['root']['size'], data['root']['filesystem'], last_partition())
+		self.partitions.append(self.root)
 
 		super(MBRPartitionMap, self).__init__()