diff --git a/clients/c/cosmopolite.c b/clients/c/cosmopolite.c
index c9e2190..4ca15e5 100644
--- a/clients/c/cosmopolite.c
+++ b/clients/c/cosmopolite.c
@@ -321,7 +321,7 @@ static void cosmo_complete_subscribe(cosmo *instance, struct cosmo_command *comm
 
   if (strcmp(result, "ok")) {
     cosmo_remove_subscription(instance, subject);
-    promise_fail(command->promise, NULL);
+    promise_fail(command->promise, NULL, NULL);
     return;
   }
 
@@ -333,20 +333,27 @@ static void cosmo_complete_subscribe(cosmo *instance, struct cosmo_command *comm
   }
   assert(!pthread_mutex_unlock(&instance->lock));
 
-  promise_succeed(command->promise, NULL);
+  promise_succeed(command->promise, NULL, NULL);
 }
 
 static void cosmo_complete_unsubscribe(cosmo *instance, struct cosmo_command *command, json_t *response, char *result) {
-  promise_complete(command->promise, NULL, (strcmp(result, "ok") == 0));
+  promise_complete(command->promise, NULL, NULL, (strcmp(result, "ok") == 0));
 }
 
 static void cosmo_complete_send_message(cosmo *instance, struct cosmo_command *command, json_t *response, char *result) {
   json_t *message;
   int err = json_unpack(response, "{so}", "message", &message);
   if (err || strcmp(result, "ok")) {
-    promise_fail(command->promise, NULL);
+    promise_fail(command->promise, NULL, NULL);
   } else {
-    promise_succeed(command->promise, message);
+    char *message_content;
+    assert(!json_unpack(message, "{ss}", "message", &message_content));
+    json_t *message_object = json_loads(message_content, JSON_DECODE_ANY, NULL);
+    assert(message_object);
+    json_object_set_new(message, "message", message_object);
+
+    json_incref(message);
+    promise_succeed(command->promise, message, (promise_cleanup) json_decref);
   }
 }
 
diff --git a/clients/c/promise.c b/clients/c/promise.c
index a980c29..8c25760 100644
--- a/clients/c/promise.c
+++ b/clients/c/promise.c
@@ -5,7 +5,6 @@
 #include "promise.h"
 
 struct promise {
-  bool will_wait;
   promise_callback on_success;
   promise_callback on_failure;
   void *passthrough;
@@ -16,11 +15,11 @@ struct promise {
 
   bool success;
   void *result;
+  promise_cleanup cleanup;
 };
 
-promise *promise_create(bool will_wait, promise_callback on_success, promise_callback on_failure, void *passthrough) {
+promise *promise_create(promise_callback on_success, promise_callback on_failure, void *passthrough) {
   promise *promise_obj = malloc(sizeof(*promise_obj));
-  promise_obj->will_wait = will_wait;
   promise_obj->on_success = on_success;
   promise_obj->on_failure = on_failure;
   promise_obj->passthrough = passthrough;
@@ -31,32 +30,35 @@ promise *promise_create(bool will_wait, promise_callback on_success, promise_cal
   return promise_obj;
 }
 
-static void promise_destroy(promise *promise_obj) {
+void promise_destroy(promise *promise_obj) {
   assert(!pthread_mutex_destroy(&promise_obj->lock));
   assert(!pthread_cond_destroy(&promise_obj->cond));
+  if (promise_obj->result && promise_obj->cleanup) {
+    promise_obj->cleanup(promise_obj->result);
+  }
   free(promise_obj);
 }
 
 bool promise_wait(promise *promise_obj, void **result) {
   assert(promise_obj);
   assert(!pthread_mutex_lock(&promise_obj->lock));
-  assert(promise_obj->will_wait);
   while (!promise_obj->fulfilled) {
     pthread_cond_wait(&promise_obj->cond, &promise_obj->lock);
   }
   assert(!pthread_mutex_unlock(&promise_obj->lock));
 
-  // promise_obj is now filled in, and owned solely by us.
   bool success = promise_obj->success;
   if (result) {
     *result = promise_obj->result;
   }
-  promise_destroy(promise_obj);
   return success;
 }
 
-void promise_complete(promise *promise_obj, void *result, bool success) {
+void promise_complete(promise *promise_obj, void *result, promise_cleanup cleanup, bool success) {
   if (!promise_obj) {
+    if (result && cleanup) {
+      cleanup(result);
+    }
     return;
   }
 
@@ -68,24 +70,18 @@ void promise_complete(promise *promise_obj, void *result, bool success) {
     promise_obj->on_failure(promise_obj->passthrough, result);
   }
 
-  if (promise_obj->will_wait) {
-    // We don't own promise_obj; pass to promise_wait()
-    promise_obj->result = result;
-    promise_obj->success = success;
-    promise_obj->fulfilled = true;
-    assert(!pthread_cond_signal(&promise_obj->cond));
-    assert(!pthread_mutex_unlock(&promise_obj->lock));
-  } else {
-    // We own promise_obj
-    assert(!pthread_mutex_unlock(&promise_obj->lock));
-    promise_destroy(promise_obj);
-  }
+  promise_obj->result = result;
+  promise_obj->cleanup = cleanup;
+  promise_obj->success = success;
+  promise_obj->fulfilled = true;
+  assert(!pthread_cond_signal(&promise_obj->cond));
+  assert(!pthread_mutex_unlock(&promise_obj->lock));
 }
 
-void promise_succeed(promise *promise_obj, void *result) {
-  promise_complete(promise_obj, result, true);
+void promise_succeed(promise *promise_obj, void *result, promise_cleanup cleanup) {
+  promise_complete(promise_obj, result, cleanup, true);
 }
 
-void promise_fail(promise *promise_obj, void *result) {
-  promise_complete(promise_obj, result, false);
+void promise_fail(promise *promise_obj, void *result, promise_cleanup cleanup) {
+  promise_complete(promise_obj, result, cleanup, false);
 }
diff --git a/clients/c/promise.h b/clients/c/promise.h
index 0303dfc..862e100 100644
--- a/clients/c/promise.h
+++ b/clients/c/promise.h
@@ -7,13 +7,15 @@ typedef struct promise promise;
 
 // (passthrough, result)
 typedef void (*promise_callback)(void *, void *);
+typedef void (*promise_cleanup)(void *);
 
-promise *promise_create(bool will_wait, promise_callback on_success, promise_callback on_failure, void *passthrough);
+promise *promise_create(promise_callback on_success, promise_callback on_failure, void *passthrough);
 bool promise_wait(promise *promise_obj, void **result);
+void promise_destroy(promise *promise_obj);
 
-void promise_complete(promise *promise_obj, void *result, bool success);
+void promise_complete(promise *promise_obj, void *result, promise_cleanup cleanup, bool success);
 // Shortcuts for promise_complete()
-void promise_succeed(promise *promise_obj, void *result);
-void promise_fail(promise *promise_obj, void *result);
+void promise_succeed(promise *promise_obj, void *result, promise_cleanup cleanup);
+void promise_fail(promise *promise_obj, void *result, promise_cleanup cleanup);
 
 #endif
diff --git a/clients/c/test.c b/clients/c/test.c
index 3c73535..b43d59f 100644
--- a/clients/c/test.c
+++ b/clients/c/test.c
@@ -306,6 +306,27 @@ bool test_complex_object(test_state *state) {
   return true;
 }
 
+bool test_send_message_promise(test_state *state) {
+  cosmo *client = create_client(state);
+
+  json_t *subject = random_subject(NULL, NULL);
+  json_t *message_out = random_message();
+
+  promise *promise_obj = promise_create(NULL, NULL, NULL);
+  cosmo_send_message(client, subject, message_out, promise_obj);
+  json_t *result;
+  assert(promise_wait(promise_obj, (void **) &result));
+  assert(json_equal(subject, json_object_get(result, "subject")));
+  assert(json_equal(message_out, json_object_get(result, "message")));
+  promise_destroy(promise_obj);
+
+  json_decref(subject);
+  json_decref(message_out);
+
+  cosmo_shutdown(client);
+  return true;
+}
+
 bool test_getmessages_subscribe(test_state *state) {
   cosmo *client = create_client(state);
 
@@ -350,6 +371,7 @@ int main(int argc, char *argv[]) {
   RUN_TEST(test_reconnect);
   RUN_TEST(test_bulk_subscribe);
   RUN_TEST(test_complex_object);
+  RUN_TEST(test_send_message_promise);
   RUN_TEST(test_getmessages_subscribe);
   RUN_TEST(test_resubscribe);