diff --git a/lily/skyline.cc b/lily/skyline.cc
index 5297f63..362fbba 100644
--- a/lily/skyline.cc
+++ b/lily/skyline.cc
@@ -45,6 +45,7 @@
 /* If we start including very thin buildings, numerical accuracy errors can
    arise. Therefore, we ignore all buildings that are less than epsilon wide. */
 #define EPS 1e-5
+#define EPSNULL 1e-12
 
 static void
 print_buildings (list<Building> const &b)
@@ -215,6 +216,9 @@ Skyline::internal_merge_skyline (list<Building> *s1, list<Building> *s2,
       if (end >= s1->front ().end_)
 	s1->pop_front ();
 
+      if (abs (end - x) < EPSNULL)
+	break;
+
       x = end;
     }
   result->reverse ();