diff --git a/SeeSharp/Integrators/Bidir/VertexConnectionAndMerging.cs b/SeeSharp/Integrators/Bidir/VertexConnectionAndMerging.cs
index d403f09..dbee096 100644
--- a/SeeSharp/Integrators/Bidir/VertexConnectionAndMerging.cs
+++ b/SeeSharp/Integrators/Bidir/VertexConnectionAndMerging.cs
@@ -267,7 +267,8 @@ public override void Render(Scene scene)
         }
     }
 
-    Stopwatch mergeBuildTimer;
+    /// <summary>Accumulates the photon-map build time across iterations; reported as MergeAccelBuildTime.</summary>
+    protected Stopwatch mergeBuildTimer;
 
     /// <summary>
     /// Generates the acceleration structure for merging