diff --git a/modules/libcom/src/osi/os/RTEMS-score/epicsAtomicOSD.h b/modules/libcom/src/osi/os/RTEMS-score/epicsAtomicOSD.h
index 510bdbc7c..b92afafe4 100644
--- a/modules/libcom/src/osi/os/RTEMS-score/epicsAtomicOSD.h
+++ b/modules/libcom/src/osi/os/RTEMS-score/epicsAtomicOSD.h
@@ -35,11 +35,11 @@ extern "C" {
 #ifndef EPICS_ATOMIC_READ_MEMORY_BARRIER
 EPICS_ATOMIC_INLINE void epicsAtomicReadMemoryBarrier (void)
 {
-    epicsAtomicMemoryBarrierFallback();
+    rbarr();
 }
 #endif
 
-#ifndef EPICS_ATOMIC_READ_MEMORY_BARRIER
+#ifndef EPICS_ATOMIC_WRITE_MEMORY_BARRIER
 EPICS_ATOMIC_INLINE void epicsAtomicWriteMemoryBarrier (void)
 {
     rwbarr();
diff --git a/modules/libcom/src/osi/os/posix/epicsAtomicOSD.h b/modules/libcom/src/osi/os/posix/epicsAtomicOSD.h
index 7a555d9d9..7cf2352be 100644
--- a/modules/libcom/src/osi/os/posix/epicsAtomicOSD.h
+++ b/modules/libcom/src/osi/os/posix/epicsAtomicOSD.h
@@ -38,7 +38,7 @@ EPICS_ATOMIC_INLINE void epicsAtomicReadMemoryBarrier (void)
 }
 #endif
 
-#ifndef EPICS_ATOMIC_READ_MEMORY_BARRIER
+#ifndef EPICS_ATOMIC_WRITE_MEMORY_BARRIER
 EPICS_ATOMIC_INLINE void epicsAtomicWriteMemoryBarrier (void)
 {
     epicsAtomicMemoryBarrierFallback();