diff --git a/src/libCom/osi/os/default/epicsAtomicOSD.c b/src/libCom/osi/os/RTEMS/epicsAtomicOSD.cpp
similarity index 100%
rename from src/libCom/osi/os/default/epicsAtomicOSD.c
rename to src/libCom/osi/os/RTEMS/epicsAtomicOSD.cpp
diff --git a/src/libCom/osi/os/default/epicsAtomicOSD.cpp b/src/libCom/osi/os/default/epicsAtomicOSD.cpp
new file mode 100644
index 000000000..e69de29bb