diff --git a/src/sgfParser/collection.py b/src/sgfParser/collection.py
--- a/src/sgfParser/collection.py
+++ b/src/sgfParser/collection.py
@@ -30,7 +30,7 @@ class GameTree:
 		if i>=len(s) or s[i]!="(":
 			# print("error when parsing GameTree")
 			return (start,None)
-		i,x=Node.create(s,start+1)
+		i,x=Node.create(s,i+1)
 		if x is None:
 			# print("error when parsing GameTree")
 			return (i,None)
@@ -67,14 +67,19 @@ class GameTree:
 			return self.nodes[i]
 		return None
 
-	## Create and return a new GameTree containing the provided Node.
+	## Create and return a new game tree containing the provided Node.
 	#
-	# The Node objects are shared between the trees, not copied.
-	def _buildSubtree(self,node):
-		res=GameTree()
+	# Ancestor nodes are copied, descendants are taken directly.
+	def _buildSubtree(self,seedNode):
+		node=seedNode.copy()
 
-		return res
-		# chci celou cestu ke kořeni a všechny podstromy nodu
+		while node.parent:
+			newNode=node.parent.copy()
+			node.parent=newNode
+			newNode.setChildren([node])
+			node=newNode
+
+		return node
 
 	## Find and yield Game Info nodes.
 	def _listGINodes(self):