diff -r fc897b7bfa7b -r 20dcc0dce64b graphics/FBD_Objects.py
--- a/graphics/FBD_Objects.py	Wed Jun 06 17:54:33 2007 +0200
+++ b/graphics/FBD_Objects.py	Mon Jun 11 14:56:25 2007 +0200
@@ -151,6 +151,8 @@
                     for i in xrange(self.Extension - len(blocktype["inputs"])):
                         start += 1
                         inputs.append(("IN%d"%start, inputs[-1][1], input[-1][2]))
+            else:
+                raise ValueError, "This block type isn't defined"
             self.Clean()
             # Extract the inputs properties and create the corresponding connector
             self.Inputs = []