diff --git a/src/libCom/osi/os/RTEMS/osdTime.cpp b/src/libCom/osi/os/RTEMS/osdTime.cpp
index 36d22c8ee..29c606383 100644
--- a/src/libCom/osi/os/RTEMS/osdTime.cpp
+++ b/src/libCom/osi/os/RTEMS/osdTime.cpp
@@ -14,6 +14,7 @@
 #include <epicsStdio.h>
 #include <rtems.h>
 #include <errno.h>
+#include <unistd.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>