diff -r ec153828ded2 -r b789b695b5c6 editors/SFCViewer.py
--- a/editors/SFCViewer.py	Tue Aug 15 12:17:51 2017 +0300
+++ b/editors/SFCViewer.py	Tue Aug 15 15:50:30 2017 +0300
@@ -341,9 +341,9 @@
         return blockName
 
     # This method check the IEC 61131-3 compatibility between two SFC blocks
-    def BlockCompatibility(self,startblock = None, endblock = None, direction = None):
-        if startblock!= None and endblock != None and (isinstance(startblock,SFC_Objects)\
-                                                               or isinstance(endblock,SFC_Objects)):
+    def BlockCompatibility(self, startblock = None, endblock = None, direction = None):
+        if startblock!= None and endblock != None and (isinstance(startblock, SFC_Objects)\
+                                                               or isinstance(endblock, SFC_Objects)):
             # Full "SFC_StandardRules" table would be symmetrical and
             # to avoid duplicate records and minimize the table only upper part is defined.
             if (direction == SOUTH or direction == EAST):