diff --git a/apps/apps.c b/apps/apps.c
index 153e723dc..cf6891176 100644
--- a/apps/apps.c
+++ b/apps/apps.c
@@ -109,7 +109,7 @@
  *
  */
 
-#ifndef _POSIX_C_SOURCE
+#if !defined(_POSIX_C_SOURCE) && defined(OPENSSL_SYS_VMS)
 #define _POSIX_C_SOURCE 2	/* On VMS, you need to define this to get
 				   the declaration of fileno().  The value
 				   2 is to make sure no function defined
diff --git a/crypto/ui/ui_openssl.c b/crypto/ui/ui_openssl.c
index 1bc25f48d..5832a73cf 100644
--- a/crypto/ui/ui_openssl.c
+++ b/crypto/ui/ui_openssl.c
@@ -122,7 +122,7 @@
  * sigaction and fileno included. -pedantic would be more appropriate for
  * the intended purposes, but we can't prevent users from adding -ansi.
  */
-#ifndef _POSIX_C_SOURCE
+#if !defined(_POSIX_C_SOURCE) && defined(OPENSSL_SYS_VMS)
 #define _POSIX_C_SOURCE 2
 #endif
 #include <signal.h>