diff --git a/ompi/mca/coll/libnbc/coll_libnbc.h b/ompi/mca/coll/libnbc/coll_libnbc.h
index 724b86d678a..b66ce60fa5e 100644
--- a/ompi/mca/coll/libnbc/coll_libnbc.h
+++ b/ompi/mca/coll/libnbc/coll_libnbc.h
@@ -13,7 +13,7 @@
  * Copyright (c) 2008      Cisco Systems, Inc.  All rights reserved.
  * Copyright (c) 2013-2015 Los Alamos National Security, LLC. All rights
  *                         reserved.
- * Copyright (c) 2014-2015 Research Organization for Information Science
+ * Copyright (c) 2014-2016 Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
  * Copyright (c) 2016      IBM Corporation.  All rights reserved.
  * $COPYRIGHT$
@@ -76,6 +76,7 @@ struct ompi_coll_libnbc_component_t {
     opal_list_t active_requests;
     int32_t active_comms;
     opal_atomic_lock_t progress_lock;
+    opal_mutex_t lock;
 };
 typedef struct ompi_coll_libnbc_component_t ompi_coll_libnbc_component_t;
 
diff --git a/ompi/mca/coll/libnbc/coll_libnbc_component.c b/ompi/mca/coll/libnbc/coll_libnbc_component.c
index 8670181bb71..fe8bdcc902a 100644
--- a/ompi/mca/coll/libnbc/coll_libnbc_component.c
+++ b/ompi/mca/coll/libnbc/coll_libnbc_component.c
@@ -91,6 +91,7 @@ libnbc_open(void)
 
     OBJ_CONSTRUCT(&mca_coll_libnbc_component.requests, opal_free_list_t);
     OBJ_CONSTRUCT(&mca_coll_libnbc_component.active_requests, opal_list_t);
+    OBJ_CONSTRUCT(&mca_coll_libnbc_component.lock, opal_mutex_t);
     ret = opal_free_list_init (&mca_coll_libnbc_component.requests,
                                sizeof(ompi_coll_libnbc_request_t), 8,
                                OBJ_CLASS(ompi_coll_libnbc_request_t),
@@ -115,6 +116,7 @@ libnbc_close(void)
 
     OBJ_DESTRUCT(&mca_coll_libnbc_component.requests);
     OBJ_DESTRUCT(&mca_coll_libnbc_component.active_requests);
+    OBJ_DESTRUCT(&mca_coll_libnbc_component.lock);
 
     return OMPI_SUCCESS;
 }
@@ -263,13 +265,17 @@ ompi_coll_libnbc_progress(void)
 
     if (opal_atomic_trylock(&mca_coll_libnbc_component.progress_lock)) return 0;
 
+    OPAL_THREAD_LOCK(&mca_coll_libnbc_component.lock);
     OPAL_LIST_FOREACH_SAFE(request, next, &mca_coll_libnbc_component.active_requests,
                            ompi_coll_libnbc_request_t) {
+        OPAL_THREAD_UNLOCK(&mca_coll_libnbc_component.lock);
         res = NBC_Progress(request);
         if( NBC_CONTINUE != res ) {
             /* done, remove and complete */
+            OPAL_THREAD_LOCK(&mca_coll_libnbc_component.lock);
             opal_list_remove_item(&mca_coll_libnbc_component.active_requests,
                                   &request->super.super.super);
+            OPAL_THREAD_UNLOCK(&mca_coll_libnbc_component.lock);
 
             if( OMPI_SUCCESS == res || NBC_OK == res || NBC_SUCCESS == res ) {
                 request->super.req_status.MPI_ERROR = OMPI_SUCCESS;
@@ -281,7 +287,9 @@ ompi_coll_libnbc_progress(void)
             ompi_request_complete(&request->super, true);
             OPAL_THREAD_UNLOCK(&ompi_request_lock);
         }
+        OPAL_THREAD_LOCK(&mca_coll_libnbc_component.lock);
     }
+    OPAL_THREAD_UNLOCK(&mca_coll_libnbc_component.lock);
 
     opal_atomic_unlock(&mca_coll_libnbc_component.progress_lock);
 
diff --git a/ompi/mca/coll/libnbc/nbc.c b/ompi/mca/coll/libnbc/nbc.c
index 430b506564d..7949fe1b90f 100644
--- a/ompi/mca/coll/libnbc/nbc.c
+++ b/ompi/mca/coll/libnbc/nbc.c
@@ -702,7 +702,9 @@ int NBC_Start(NBC_Handle *handle, NBC_Schedule *schedule) {
   if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) {
     return res;
   }
+  OPAL_THREAD_LOCK(&mca_coll_libnbc_component.lock);
   opal_list_append(&mca_coll_libnbc_component.active_requests, &(handle->super.super.super));
+  OPAL_THREAD_UNLOCK(&mca_coll_libnbc_component.lock);
 
   return OMPI_SUCCESS;
 }