diff --git a/src/async/context.cpp b/src/async/context.cpp
index c8f7e5f..5a5bc8c 100644
--- a/src/async/context.cpp
+++ b/src/async/context.cpp
@@ -84,6 +84,8 @@
 /* The sender for the wait/process event. */
 struct wait_process_sender
 {
+    using is_sender = void;
+
     explicit wait_process_sender(context& ctx) : ctx(ctx) {}
 
     friend auto tag_invoke(execution::get_completion_signatures_t,