diff --git a/benchmark/src/main/java/org/capnproto/benchmark/CatRank.java b/benchmark/src/main/java/org/capnproto/benchmark/CatRank.java
index 412b057..8c5bb57 100644
--- a/benchmark/src/main/java/org/capnproto/benchmark/CatRank.java
+++ b/benchmark/src/main/java/org/capnproto/benchmark/CatRank.java
@@ -62,15 +62,14 @@ public class CatRank
             int urlSize = rng.nextLessThan(100);
 
             int urlPrefixLength = URL_PREFIX.size();
-            StringBuilder url = new StringBuilder();
-            url.append(URL_PREFIX);
+            Text.Builder url = result.initUrl(urlSize + urlPrefixLength);
+            java.nio.ByteBuffer bytes = url.asByteBuffer();
+            bytes.put(URL_PREFIX.asByteBuffer());
 
             for (int j = 0; j < urlSize; j++) {
-                url.append('a' + rng.nextLessThan(26));
+                bytes.put((byte) (97 + rng.nextLessThan(26)));
             }
 
-            result.setUrl(url.toString());
-
             boolean isCat = rng.nextLessThan(8) == 0;
             boolean isDog = rng.nextLessThan(8) == 0;
             if (isCat && !isDog) {