diff --git a/FlatCAM.py b/FlatCAM.py
index 1cb60c9f..46cfc307 100644
--- a/FlatCAM.py
+++ b/FlatCAM.py
@@ -1,10 +1,13 @@
 import sys
 from PyQt4 import QtGui
-from PyQt4 import QtCore
 from FlatCAMApp import App
 
+
 def debug_trace():
-    '''Set a tracepoint in the Python debugger that works with Qt'''
+    """
+    Set a tracepoint in the Python debugger that works with Qt
+    :return: None
+    """
     from PyQt4.QtCore import pyqtRemoveInputHook
     #from pdb import set_trace
     pyqtRemoveInputHook()
@@ -12,9 +15,10 @@ def debug_trace():
 
 debug_trace()
 
-# all X11 calling should  be thread safe otherwise we have strange issues
-QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_X11InitThreads)
+# All X11 calling should be thread safe otherwise we have strange issues
+# QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_X11InitThreads)
+# NOTE: Never talk to the GUI from threads! This is why I commented the above.
 
 app = QtGui.QApplication(sys.argv)
 fc = App()
-sys.exit(app.exec_())
\ No newline at end of file
+sys.exit(app.exec_())