diff --git a/pdfminer/layout.py b/pdfminer/layout.py
index 14383f1..7e0f312 100644
--- a/pdfminer/layout.py
+++ b/pdfminer/layout.py
@@ -609,8 +609,8 @@ class LTLayoutContainer(LTContainer):
                 group = LTTextGroupLRTB([obj1,obj2])
             plane.remove(obj1)
             plane.remove(obj2)
-            dists = [ (c,d,o1,o2) for (c,d,o1,o2) in dists
-                      if o1 in plane and o2 in plane ]
+            # this line is optimized -- don't change without profiling
+            dists = [ n for n in dists if n[2] in plane._objs and n[3] in plane._objs ]
             for other in plane:
                 dists.append((0, dist(group,other), group, other))
             dists.sort()