diff --git a/src/core.py b/src/core.py
--- a/src/core.py
+++ b/src/core.py
@@ -6,7 +6,7 @@ import PIL
 from util import MsgQueue
 from gui import gui
 from imageanalyzer import ImageAnalyzer
-from go import Go
+from go import Go, isLegalPosition
 import config as cfg
 
 
@@ -47,7 +47,10 @@ class Core:
 
 	def analyze(self):
 		if self.detector.analyze(self._frame):
-			self._guiMessages.send("setGameState",(self.detector.board,))
+			if isLegalPosition(self.detector.board):
+				self._guiMessages.send("setGameState",(self.detector.board,))
+			else:
+				log.info("illegal position detected")
 
 	def listen(self):
 		listenerThread=threading.Thread(target=lambda: self._ownMessages.listen())