diff --git a/repos/os/include/os/packet_stream.h b/repos/os/include/os/packet_stream.h
index 77ae905bdb..ca43afa768 100644
--- a/repos/os/include/os/packet_stream.h
+++ b/repos/os/include/os/packet_stream.h
@@ -168,8 +168,8 @@ class Genode::Packet_descriptor_queue
 		 */
 		struct
 		{
-			unsigned          _head;
-			unsigned          _tail;
+			unsigned volatile _head;
+			unsigned volatile _tail;
 			PACKET_DESCRIPTOR _queue[QUEUE_SIZE];
 		};