diff --git a/zenoh-java/src/commonMain/kotlin/io/zenoh/bytes/ZBytes.kt b/zenoh-java/src/commonMain/kotlin/io/zenoh/bytes/ZBytes.kt
index 5822fd00..9d2927d4 100644
--- a/zenoh-java/src/commonMain/kotlin/io/zenoh/bytes/ZBytes.kt
+++ b/zenoh-java/src/commonMain/kotlin/io/zenoh/bytes/ZBytes.kt
@@ -48,10 +48,19 @@ import io.zenoh.jni.bytes.ZBytes as JniZBytes
  * dropped samples are the one place native memory can be retained.
  */
 class ZBytes private constructor(
-    private var eager: ByteArray?,
+    initialBytes: ByteArray?,
     private var handle: JniZBytes?,
 ) : IntoZBytes {
 
+    /**
+     * The materialized bytes, `null` until a handle-backed ZBytes is read.
+     * Volatile: the [bytes] getter reads it outside the monitor, so the write
+     * under the monitor must be safely published to that unlocked fast path.
+     * `handle` needs no such treatment — it is only touched inside the monitor.
+     */
+    @Volatile
+    private var eager: ByteArray? = initialBytes
+
     internal constructor(bytes: ByteArray) : this(bytes, null)
 
     /**