diff --git a/src/analyzer/corners.py b/src/analyzer/corners.py
--- a/src/analyzer/corners.py
+++ b/src/analyzer/corners.py
@@ -7,7 +7,7 @@ log=logging.getLogger(__name__)
 
 class Corners:
 	def __init__(self,cornerList=[]):
-		self._corners=cornerList[:]
+		self._corners=list(cornerList)
 		self._is_canon=False
 		self._canonizeOrder()