diff --git a/src/mpt/tests/qos/ppuserdata.c b/src/mpt/tests/qos/ppuserdata.c
index 0b319c7..4951311 100644
--- a/src/mpt/tests/qos/ppuserdata.c
+++ b/src/mpt/tests/qos/ppuserdata.c
@@ -27,8 +27,8 @@ MPT_Test(qos, ppuserdata, .init=ppud_init, .fini=ppud_fini);
 /*
  * Checks whether reader/writer user_data QoS changes work.
  */
-#define TEST_A_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwuserdata", true, 10, RWUD_USERDATA)
-#define TEST_B_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwuserdata", false, 0, RWUD_USERDATA)
+#define TEST_A_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwuserdata", true, 10, RWUD_USERDATA, NULL)
+#define TEST_B_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwuserdata", false, 0, RWUD_USERDATA, NULL)
 MPT_TestProcess(qos, rwuserdata, a, rwud, TEST_A_ARGS);
 MPT_TestProcess(qos, rwuserdata, b, rwud, TEST_B_ARGS);
 MPT_Test(qos, rwuserdata, .init=ppud_init, .fini=ppud_fini);
@@ -38,8 +38,8 @@ MPT_Test(qos, rwuserdata, .init=ppud_init, .fini=ppud_fini);
 /*
  * Checks whether topic_data QoS changes become visible in reader/writer.
  */
-#define TEST_A_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwtopicdata", true, 10, RWUD_TOPICDATA)
-#define TEST_B_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwtopicdata", false, 0, RWUD_TOPICDATA)
+#define TEST_A_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwtopicdata", true, 10, RWUD_TOPICDATA, NULL)
+#define TEST_B_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwtopicdata", false, 0, RWUD_TOPICDATA, NULL)
 MPT_TestProcess(qos, rwtopicdata, a, rwud, TEST_A_ARGS);
 MPT_TestProcess(qos, rwtopicdata, b, rwud, TEST_B_ARGS);
 MPT_Test(qos, rwtopicdata, .init=ppud_init, .fini=ppud_fini);
@@ -49,10 +49,23 @@ MPT_Test(qos, rwtopicdata, .init=ppud_init, .fini=ppud_fini);
 /*
  * Checks whether group_data QoS changes become visible in reader/writer.
  */
-#define TEST_A_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwgroupdata", true, 10, RWUD_GROUPDATA)
-#define TEST_B_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwgroupdata", false, 0, RWUD_GROUPDATA)
+#define TEST_A_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwgroupdata", true, 10, RWUD_GROUPDATA, NULL)
+#define TEST_B_ARGS MPT_ArgValues(DDS_DOMAIN_DEFAULT, "rwgroupdata", false, 0, RWUD_GROUPDATA, NULL)
 MPT_TestProcess(qos, rwgroupdata, a, rwud, TEST_A_ARGS);
 MPT_TestProcess(qos, rwgroupdata, b, rwud, TEST_B_ARGS);
 MPT_Test(qos, rwgroupdata, .init=ppud_init, .fini=ppud_fini);
 #undef TEST_A_ARGS
 #undef TEST_B_ARGS
+
+/*
+ * Checks whether topic_data QoS changes become visible in reader/writer,
+ * but doing so in 2 domains simultaneously -- the specified domain id,
+ * and the one immediately above that
+ */
+#define TEST_A_ARGS MPT_ArgValues(3, "rwtopicdataM", true, 10, RWUD_TOPICDATA)
+#define TEST_B_ARGS MPT_ArgValues(3, "rwtopicdataM", false, 0, RWUD_TOPICDATA)
+MPT_TestProcess(qos, rwtopicdataM, a, rwudM, TEST_A_ARGS);
+MPT_TestProcess(qos, rwtopicdataM, b, rwudM, TEST_B_ARGS);
+MPT_Test(qos, rwtopicdataM, .init=ppud_init, .fini=ppud_fini);
+#undef TEST_A_ARGS
+#undef TEST_B_ARGS
diff --git a/src/mpt/tests/qos/procs/ppud.c b/src/mpt/tests/qos/procs/ppud.c
index 31c8da4..25ae30a 100644
--- a/src/mpt/tests/qos/procs/ppud.c
+++ b/src/mpt/tests/qos/procs/ppud.c
@@ -18,6 +18,8 @@
 #include "dds/dds.h"
 
 #include "dds/ddsrt/time.h"
+#include "dds/ddsrt/threads.h"
+#include "dds/ddsrt/sync.h"
 #include "dds/ddsrt/process.h"
 #include "dds/ddsrt/sockets.h"
 #include "dds/ddsrt/heap.h"
@@ -161,16 +163,42 @@ MPT_ProcessEntry (ppud,
 #undef prefix
 }
 
-static const char *exp_rwud[] = {
-  "a", "bc", "def", ""
+static const char *exp_rwud[2][4] = {
+  { "a", "bc", "def", "" },
+  { "p", "qr", "stu", "" }
 };
 
+struct rwud_barrier {
+  ddsrt_mutex_t lock;
+  ddsrt_cond_t cond;
+  int initcount;
+  int count;
+};
+
+static void barrierwait (struct rwud_barrier *barrier, int id)
+{
+  printf ("%d waiting at barrier\n", id);
+  fflush (stdout);
+  ddsrt_mutex_lock (&barrier->lock);
+  assert (barrier->initcount > 0);
+  if (barrier->count == 0)
+    barrier->count = barrier->initcount;
+  if (--barrier->count == 0)
+    ddsrt_cond_broadcast (&barrier->cond);
+  while (barrier->count > 0)
+    ddsrt_cond_wait (&barrier->cond, &barrier->lock);
+  ddsrt_mutex_unlock (&barrier->lock);
+  printf ("%d continuing past barrier\n", id);
+  fflush (stdout);
+}
+
 MPT_ProcessEntry (rwud,
                   MPT_Args (dds_domainid_t domainid,
                             const char *topic_name,
                             bool master,
                             unsigned ncycles,
-                            enum rwud which))
+                            enum rwud which,
+                            struct rwud_barrier *barrier))
 {
   bool (*qget) (const dds_qos_t * __restrict qos, void **value, size_t *sz) = 0;
   void (*qset) (dds_qos_t * __restrict qos, const void *value, size_t sz) = 0;
@@ -247,8 +275,14 @@ MPT_ProcessEntry (rwud,
     MPT_ASSERT_EQ (rc, DDS_RETCODE_OK, "Set QoS failed: %s\n", dds_strretcode (rc));
   }
 
+  if (barrier)
+  {
+    barrierwait (barrier, id);
+  }
+
   bool done = false;
   bool synced = !master;
+  const unsigned exp_setindex = (unsigned) domainid % 2;
   unsigned exp_index = 0;
   unsigned exp_cycle = 0;
   dds_instance_handle_t peer = 0;
@@ -290,7 +324,7 @@ MPT_ProcessEntry (rwud,
                     id, exp_index, expusz, expud, usz, ud ? (char *) ud : "(null)");
             MPT_ASSERT (eq, "%s mismatch: expected %u %zu/%s received %zu/%s\n",
                         qname, exp_index, expusz, expud ? expud : "(null)", usz, ud ? (char *) ud : "(null)");
-            if (++exp_index == sizeof (exp_rwud) / sizeof (exp_rwud[0]))
+            if (++exp_index == sizeof (exp_rwud[0]) / sizeof (exp_rwud[0][0]))
             {
               exp_index = 0;
               exp_cycle++;
@@ -299,7 +333,7 @@ MPT_ProcessEntry (rwud,
             if (exp_cycle == ncycles)
               done = true;
 
-            expud = exp_rwud[exp_index];
+            expud = exp_rwud[exp_setindex][exp_index];
             expusz = strlen (expud);
           }
           else
@@ -335,7 +369,80 @@ MPT_ProcessEntry (rwud,
     fflush (stdout);
   }
   dds_delete_qos (qos);
+
+  if (barrier)
+  {
+    barrierwait (barrier, id);
+  }
+
   rc = dds_delete (dp);
   MPT_ASSERT_EQ (rc, DDS_RETCODE_OK, "teardown failed\n");
   printf ("=== [Check(%d)] Done\n", id);
 }
+
+struct rwudM_thread_arg {
+  dds_domainid_t domainid;
+  const char *topic_name;
+  bool master;
+  unsigned ncycles;
+  enum rwud which;
+  mpt_retval_t retval;
+  struct rwud_barrier *barrier;
+  const mpt_data_t *mpt__args__;
+};
+
+static uint32_t rwudM_thread (void *varg)
+{
+  struct rwudM_thread_arg *arg = varg;
+  const mpt_data_t *mpt__args__ = arg->mpt__args__;
+  mpt_retval_t *mpt__retval__ = &arg->retval;
+  MPT_ProcessEntryName(rwud) (MPT_ArgValues (arg->domainid, arg->topic_name, arg->master, arg->ncycles, arg->which, arg->barrier));
+  return 0;
+}
+
+MPT_ProcessEntry (rwudM,
+                  MPT_Args (dds_domainid_t domainid,
+                            const char *topic_name,
+                            bool master,
+                            unsigned ncycles,
+                            enum rwud which))
+{
+  dds_return_t ret;
+  uint32_t dummy;
+  ddsrt_thread_t thr[2];
+  ddsrt_threadattr_t attr;
+  struct rwud_barrier barrier;
+  struct rwudM_thread_arg a = {
+    .domainid = domainid,
+    .topic_name = topic_name,
+    .master = master,
+    .ncycles = ncycles,
+    .which = which,
+    .barrier = &barrier,
+    .retval = MPT_SUCCESS,
+    .mpt__args__ = mpt__args__
+  };
+  struct rwudM_thread_arg b;
+  b = a; ++b.domainid;
+
+  ddsrt_mutex_init (&barrier.lock);
+  ddsrt_cond_init (&barrier.cond);
+  barrier.initcount = 2;
+  barrier.count = 0;
+
+  ddsrt_threadattr_init (&attr);
+  ret = ddsrt_thread_create (&thr[0], "a", &attr, &rwudM_thread, &a);
+  MPT_ASSERT_FATAL_EQ (ret, DDS_RETCODE_OK, "failed to create thread a\n");
+  ret = ddsrt_thread_create (&thr[1], "b", &attr, &rwudM_thread, &b);
+  MPT_ASSERT_FATAL_EQ (ret, DDS_RETCODE_OK, "failed to create thread b\n");
+  ret = ddsrt_thread_join (thr[0], &dummy);
+  MPT_ASSERT_FATAL_EQ (ret, DDS_RETCODE_OK, "failed to join thread a\n");
+  ret = ddsrt_thread_join (thr[1], &dummy);
+  MPT_ASSERT_FATAL_EQ (ret, DDS_RETCODE_OK, "failed to join thread b\n");
+  /* forward thread failures to process failures */
+  MPT_ASSERT_EQ (a.retval, MPT_SUCCESS, "thread a failed\n");
+  MPT_ASSERT_EQ (b.retval, MPT_SUCCESS, "thread b failed\n");
+
+  ddsrt_cond_destroy (&barrier.cond);
+  ddsrt_mutex_destroy (&barrier.lock);
+}
diff --git a/src/mpt/tests/qos/procs/ppud.h b/src/mpt/tests/qos/procs/ppud.h
index 8f8e012..598cc59 100644
--- a/src/mpt/tests/qos/procs/ppud.h
+++ b/src/mpt/tests/qos/procs/ppud.h
@@ -32,12 +32,22 @@ enum rwud {
   RWUD_TOPICDATA
 };
 
+struct rwud_barrier;
+
 MPT_ProcessEntry (ppud,
                   MPT_Args (dds_domainid_t domainid,
                             bool master,
                             unsigned ncycles));
 
 MPT_ProcessEntry (rwud,
+                  MPT_Args (dds_domainid_t domainid,
+                            const char *topic_name,
+                            bool master,
+                            unsigned ncycles,
+                            enum rwud which,
+                            struct rwud_barrier *barrier));
+
+MPT_ProcessEntry (rwudM,
                   MPT_Args (dds_domainid_t domainid,
                             const char *topic_name,
                             bool master,