diff --git a/tests/perf/org/jgroups/tests/perf/UPerf.java b/tests/perf/org/jgroups/tests/perf/UPerf.java
index bb6cff100e4..97b8c33562e 100644
--- a/tests/perf/org/jgroups/tests/perf/UPerf.java
+++ b/tests/perf/org/jgroups/tests/perf/UPerf.java
@@ -456,7 +456,7 @@ public int estimatedSize(Object arg) {
             if(arg == null)
                 return 2;
             if(arg instanceof byte[])
-                return msg_size;
+                return msg_size + 24;
             if(arg instanceof Long)
                 return 10;
             return 50;