diff --git a/src/libCom/osi/os/default/osdEnv.c b/src/libCom/osi/os/default/osdEnv.c
index 27d016fc8..9ff9cd08f 100644
--- a/src/libCom/osi/os/default/osdEnv.c
+++ b/src/libCom/osi/os/default/osdEnv.c
@@ -19,6 +19,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <ctype.h>
+#include <errno.h>
 
 #define epicsExportSharedSymbols
 #include <errlog.h>