diff --git a/ompi/mca/osc/rdma/osc_rdma.c b/ompi/mca/osc/rdma/osc_rdma.c
index 7fd313028a..f8ea6eaf87 100644
--- a/ompi/mca/osc/rdma/osc_rdma.c
+++ b/ompi/mca/osc/rdma/osc_rdma.c
@@ -89,6 +89,12 @@ ompi_osc_rdma_free(ompi_win_t *win)
 
     OBJ_DESTRUCT(&module->pending_acc);
 
+    while (NULL != (item = opal_list_remove_first (&module->pending_posts))) {
+        OBJ_RELEASE(item);
+    }
+
+    OBJ_DESTRUCT(&module->pending_posts);
+
     osc_rdma_gc_clean ();
 
     if (NULL != module->peers) {
diff --git a/ompi/mca/osc/rdma/osc_rdma.h b/ompi/mca/osc/rdma/osc_rdma.h
index 472c70426c..0f91b4141d 100644
--- a/ompi/mca/osc/rdma/osc_rdma.h
+++ b/ompi/mca/osc/rdma/osc_rdma.h
@@ -201,6 +201,10 @@ struct ompi_osc_rdma_module_t {
     /* enforce accumulate semantics */
     opal_atomic_lock_t accumulate_lock;
     opal_list_t        pending_acc;
+
+    /* enforce pscw matching */
+    /** list of unmatched post messages */
+    opal_list_t        pending_posts;
 };
 typedef struct ompi_osc_rdma_module_t ompi_osc_rdma_module_t;
 OMPI_MODULE_DECLSPEC extern ompi_osc_rdma_component_t mca_osc_rdma_component;
@@ -328,7 +332,7 @@ int ompi_osc_rdma_rget_accumulate(void *origin_addr,
 int ompi_osc_rdma_fence(int assert, struct ompi_win_t *win);
 
 /* received a post message */
-int osc_rdma_incoming_post (ompi_osc_rdma_module_t *module);
+int osc_rdma_incoming_post (ompi_osc_rdma_module_t *module, int source);
 
 int ompi_osc_rdma_start(struct ompi_group_t *group,
                         int assert,
diff --git a/ompi/mca/osc/rdma/osc_rdma_active_target.c b/ompi/mca/osc/rdma/osc_rdma_active_target.c
index b31141563d..2b0f34121f 100644
--- a/ompi/mca/osc/rdma/osc_rdma_active_target.c
+++ b/ompi/mca/osc/rdma/osc_rdma_active_target.c
@@ -32,6 +32,21 @@
 #include "ompi/communicator/communicator.h"
 #include "ompi/mca/osc/base/base.h"
 
+/**
+ * ompi_osc_rdma_pending_post_t:
+ *
+ * Describes a post operation that was encountered outside it's
+ * matching start operation.
+ */
+struct ompi_osc_rdma_pending_post_t {
+    opal_list_item_t super;
+    int rank;
+};
+typedef struct ompi_osc_rdma_pending_post_t ompi_osc_rdma_pending_post_t;
+OBJ_CLASS_DECLARATION(ompi_osc_rdma_pending_post_t);
+
+OBJ_CLASS_INSTANCE(ompi_osc_rdma_pending_post_t, opal_list_item_t, NULL, NULL);
+
 static int*
 get_comm_ranks(ompi_osc_rdma_module_t *module,
                ompi_group_t *sub_group)
@@ -153,6 +168,7 @@ ompi_osc_rdma_start(ompi_group_t *group,
                     ompi_win_t *win)
 {
     ompi_osc_rdma_module_t *module = GET_MODULE(win);
+    ompi_osc_rdma_pending_post_t *pending_post, *next;
 
     OPAL_OUTPUT_VERBOSE((50, ompi_osc_base_framework.framework_output,
                          "ompi_osc_rdma_start entering..."));
@@ -171,6 +187,22 @@ ompi_osc_rdma_start(ompi_group_t *group,
 
     module->sc_group = group;    
 
+    OPAL_LIST_FOREACH_SAFE(pending_post, next, &module->pending_posts, ompi_osc_rdma_pending_post_t) {
+        ompi_proc_t *pending_proc = ompi_comm_peer_lookup (module->comm, pending_post->rank);
+        int group_size = ompi_group_size (module->sc_group);
+
+        for (int i = 0 ; i < group_size ; ++i) {
+            ompi_proc_t *group_proc = ompi_group_peer_lookup (module->sc_group, i);
+
+            if (group_proc == pending_proc) {
+                ++module->num_post_msgs;
+                opal_list_remove_item (&module->pending_posts, &pending_post->super);
+                OBJ_RELEASE(pending_post);
+                break;
+            }
+        }
+    }
+
     /* disable eager sends until we've receved the proper number of
        post messages, at which time we know all our peers are ready to
        receive messages. */
@@ -434,3 +466,46 @@ ompi_osc_rdma_test(ompi_win_t *win,
     return ret;
 }
 
+int osc_rdma_incoming_post (ompi_osc_rdma_module_t *module, int source)
+{
+    ompi_proc_t *source_proc = ompi_comm_peer_lookup (module->comm, source);
+    bool matched = false;
+
+    OPAL_THREAD_LOCK(&module->lock);
+
+    if (module->sc_group) {
+        const int group_size = ompi_group_size (module->sc_group);
+
+        for (int i = 0 ; i < group_size ; ++i) {
+            ompi_proc_t *group_proc = ompi_group_peer_lookup (module->sc_group, i);
+
+            if (group_proc == source_proc) {
+                matched = true;
+                break;
+            }
+        }
+    }
+
+    if (!matched) {
+        ompi_osc_rdma_pending_post_t *pending_post = OBJ_NEW(ompi_osc_rdma_pending_post_t);
+
+        pending_post->rank = source;
+
+        opal_list_append (&module->pending_posts, &pending_post->super);
+
+        OPAL_THREAD_UNLOCK(&module->lock);
+        return OMPI_SUCCESS;
+    }
+
+    module->num_post_msgs++;
+    OPAL_OUTPUT_VERBOSE((50, ompi_osc_base_framework.framework_output,
+                         "received post message. num_post_msgs = %d", module->num_post_msgs));
+
+    if (0 == module->num_post_msgs) {
+        module->active_eager_send_active = true;
+    }
+    opal_condition_broadcast (&module->cond);
+    OPAL_THREAD_UNLOCK(&module->lock);
+
+    return OMPI_SUCCESS;
+}
diff --git a/ompi/mca/osc/rdma/osc_rdma_component.c b/ompi/mca/osc/rdma/osc_rdma_component.c
index 42995338a5..a817cb67f4 100644
--- a/ompi/mca/osc/rdma/osc_rdma_component.c
+++ b/ompi/mca/osc/rdma/osc_rdma_component.c
@@ -356,6 +356,7 @@ component_select(struct ompi_win_t *win, void **base, size_t size, int disp_unit
     OBJ_CONSTRUCT(&module->locks_pending, opal_list_t);
     OBJ_CONSTRUCT(&module->outstanding_locks, opal_list_t);
     OBJ_CONSTRUCT(&module->pending_acc, opal_list_t);
+    OBJ_CONSTRUCT(&module->pending_posts, opal_list_t);
 
     /* options */
     /* FIX ME: should actually check this value... */
diff --git a/ompi/mca/osc/rdma/osc_rdma_data_move.c b/ompi/mca/osc/rdma/osc_rdma_data_move.c
index 5123558905..f4e8d21399 100644
--- a/ompi/mca/osc/rdma/osc_rdma_data_move.c
+++ b/ompi/mca/osc/rdma/osc_rdma_data_move.c
@@ -1654,7 +1654,7 @@ static int ompi_osc_rdma_callback (ompi_request_t *request)
         process_frag(module, (ompi_osc_rdma_frag_header_t *) base_header);
         break;
     case OMPI_OSC_RDMA_HDR_TYPE_POST:
-        (void) osc_rdma_incoming_post (module);
+        (void) osc_rdma_incoming_post (module, source);
         break;
     case OMPI_OSC_RDMA_HDR_TYPE_LOCK_ACK:
         ompi_osc_rdma_process_lock_ack(module, (ompi_osc_rdma_header_lock_ack_t *) base_header);
diff --git a/ompi/mca/osc/rdma/osc_rdma_frag.c b/ompi/mca/osc/rdma/osc_rdma_frag.c
index f24c1bd83d..09ef067d09 100644
--- a/ompi/mca/osc/rdma/osc_rdma_frag.c
+++ b/ompi/mca/osc/rdma/osc_rdma_frag.c
@@ -196,19 +196,3 @@ ompi_osc_rdma_frag_flush_all(ompi_osc_rdma_module_t *module)
 
     return OMPI_SUCCESS;
 }
-
-int osc_rdma_incoming_post (ompi_osc_rdma_module_t *module)
-{
-    OPAL_THREAD_LOCK(&module->lock);
-    module->num_post_msgs++;
-    OPAL_OUTPUT_VERBOSE((50, ompi_osc_base_framework.framework_output,
-                         "received post message. num_post_msgs = %d", module->num_post_msgs));
-
-    if (0 == module->num_post_msgs) {
-        module->active_eager_send_active = true;
-    }
-    opal_condition_broadcast (&module->cond);
-    OPAL_THREAD_UNLOCK(&module->lock);
-
-    return OMPI_SUCCESS;
-}