diff --git a/src/sgfParser/collection.py b/src/sgfParser/collection.py
--- a/src/sgfParser/collection.py
+++ b/src/sgfParser/collection.py
@@ -55,7 +55,7 @@ class GameTree:
 			if y: y.addChild(subroot)
 			i=skipWhitespace(s,i)
 		if i>=len(s) or s[i]!=")":
-			raise ParserError("expected end of the GameTree marked by ')'",s,i)
+			raise ParserError("expected end of a GameTree marked by ')'",s,i)
 		i=skipWhitespace(s,i+1)
 		return (i,res)