diff --git a/sop-java/src/main/kotlin/sop/util/ProxyOutputStream.kt b/sop-java/src/main/kotlin/sop/util/ProxyOutputStream.kt
index a608c89..4ba24b8 100644
--- a/sop-java/src/main/kotlin/sop/util/ProxyOutputStream.kt
+++ b/sop-java/src/main/kotlin/sop/util/ProxyOutputStream.kt
@@ -16,6 +16,7 @@ import java.io.OutputStream
  * target output stream is not yet known.
  */
 @Deprecated("Marked for removal.")
+// TODO: Remove in 11.X
 class ProxyOutputStream : OutputStream() {
     private val buffer = ByteArrayOutputStream()
     private var swapped: OutputStream? = null