Index: perspective.py
===================================================================
--- perspective.py	(revision 17895)
+++ perspective.py	(working copy)
@@ -73,7 +73,9 @@
                 f.close()
                 err.close()
             sp = array([[q['x'], q['y']+q['height']],[q['x'], q['y']],[q['x']+q['width'], q['y']],[q['x']+q['width'], q['y']+q['height']]], dtype=float64)
-
+        else:
+            inkex.debug("Second selected object should be a path, not %s" % obj.tag)
+            sys.exit()
         solmatrix = zeros((8,8), dtype=float64)
         free_term = zeros((8), dtype=float64)
         for i in (0,1,2,3):