diff --git a/ompi/mca/btl/sm/btl_sm_fifo.h b/ompi/mca/btl/sm/btl_sm_fifo.h
index 1a780ccd61..b997dc40bf 100644
--- a/ompi/mca/btl/sm/btl_sm_fifo.h
+++ b/ompi/mca/btl/sm/btl_sm_fifo.h
@@ -10,13 +10,15 @@ do {                                                                        \
     fifo=&(mca_btl_sm_component.fifo[peer_smp_rank][my_smp_rank]);          \
                                                                             \
     /* thread lock */                                                       \
-    opal_atomic_lock(fifo->head_lock);                                      \
+    if(opal_using_threads())                                                \
+        opal_atomic_lock(fifo->head_lock);                                  \
     /* post fragment */                                                     \
     while(ompi_fifo_write_to_head(hdr, fifo,                                \
         mca_btl_sm_component.sm_mpool) != OMPI_SUCCESS)                     \
         opal_progress();                                                    \
     MCA_BTL_SM_SIGNAL_PEER(endpoint_peer);                                  \
-    opal_atomic_unlock(fifo->head_lock);                                    \
+    if(opal_using_threads())                                                \
+        opal_atomic_unlock(fifo->head_lock);                                \
 } while(0) 
 
 #endif