diff --git a/lib/handshake.js b/lib/handshake.js
index 254837b..1abb9a4 100644
--- a/lib/handshake.js
+++ b/lib/handshake.js
@@ -46,7 +46,14 @@ function readDepths(bl, display, depths, n_depths, cb)
         var visuals = {};
         readVisuals(bl, visuals, n_visuals, function()
         {
-            depths[dep] = visuals;
+            if (dep in depths) {
+                for (var visual in visuals) {
+                    depths[dep][visual] = visuals[visual];
+                }
+                n_depths--;
+            } else {
+                depths[dep] = visuals;
+            }
             if (Object.keys(depths).length == n_depths)
                 cb();
             else