diff --git a/libs/ardour/playlist.cc b/libs/ardour/playlist.cc
index 94e6e421bd..cd53f35d95 100644
--- a/libs/ardour/playlist.cc
+++ b/libs/ardour/playlist.cc
@@ -1999,7 +1999,7 @@ Playlist::relayer ()
 	/* don't send multiple Modified notifications
 	   when multiple regions are relayered.
 	*/
- 
+
 	freeze ();
 
 	/* Build up a new list of regions on each layer, stored in a set of lists
@@ -2019,7 +2019,7 @@ Playlist::relayer ()
 	}
 
 	/* hence the size of each time division */
-	double const division_size = (end - start) / divisions;
+	double const division_size = (end - start) / double (divisions);
 
 	vector<vector<RegionList> > layers;
 	layers.push_back (vector<RegionList> (divisions));
@@ -2054,6 +2054,8 @@ Playlist::relayer ()
 			end_division--;
 		}
 
+		assert (end_division < divisions);
+
 		/* find the lowest layer that this region can go on */
 		size_t j = layers.size();
 		while (j > 0) {