diff --git a/common/vncauth.c b/common/vncauth.c
index 82c1b68..0b20f53 100644
--- a/common/vncauth.c
+++ b/common/vncauth.c
@@ -24,6 +24,7 @@
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
 #define _POSIX_SOURCE
+#define _XOPEN_SOURCE 600
 #endif
 #ifdef LIBVNCSERVER_HAVE_SYS_TYPES_H
 #include <sys/types.h>
diff --git a/libvncclient/rfbproto.c b/libvncclient/rfbproto.c
index 505ef50..d18459e 100644
--- a/libvncclient/rfbproto.c
+++ b/libvncclient/rfbproto.c
@@ -26,6 +26,7 @@
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
 #define _POSIX_SOURCE
+#define _XOPEN_SOURCE 600
 #endif
 #ifndef WIN32
 #include <unistd.h>
diff --git a/libvncclient/sockets.c b/libvncclient/sockets.c
index 6c47491..c97a90f 100644
--- a/libvncclient/sockets.c
+++ b/libvncclient/sockets.c
@@ -24,6 +24,11 @@
 
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
+#ifdef __linux__
+/* Setting this on other systems hides definitions such as INADDR_LOOPBACK.
+ * The check should be for __GLIBC__ in fact. */
+# define _POSIX_SOURCE
+#endif
 #endif
 #include <unistd.h>
 #include <errno.h>
diff --git a/libvncserver/httpd.c b/libvncserver/httpd.c
index ed91e46..792a52b 100644
--- a/libvncserver/httpd.c
+++ b/libvncserver/httpd.c
@@ -23,6 +23,11 @@
  *  USA.
  */
 
+#ifdef __STRICT_ANSI__
+#define _BSD_SOURCE
+#define _POSIX_SOURCE
+#endif
+
 #include <rfb/rfb.h>
 
 #include <ctype.h>
diff --git a/libvncserver/rfbserver.c b/libvncserver/rfbserver.c
index cc398f2..ad64ac1 100644
--- a/libvncserver/rfbserver.c
+++ b/libvncserver/rfbserver.c
@@ -28,6 +28,8 @@
 
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
+#define _POSIX_SOURCE
+#define _XOPEN_SOURCE 600
 #endif
 #include <string.h>
 #include <rfb/rfb.h>
diff --git a/libvncserver/sockets.c b/libvncserver/sockets.c
index 2345248..ddd8450 100644
--- a/libvncserver/sockets.c
+++ b/libvncserver/sockets.c
@@ -43,7 +43,11 @@
 
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
-#define _POSIX_SOURCE
+#ifdef __linux__
+/* Setting this on other systems hides definitions such as INADDR_LOOPBACK.
+ * The check should be for __GLIBC__ in fact. */
+# define _POSIX_SOURCE
+#endif
 #endif
 
 #include <rfb/rfb.h>
diff --git a/libvncserver/websockets.c b/libvncserver/websockets.c
index f7e3d04..043e6cb 100644
--- a/libvncserver/websockets.c
+++ b/libvncserver/websockets.c
@@ -28,7 +28,6 @@
 
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
-#define _POSIX_SOURCE
 #endif
 
 #include <rfb/rfb.h>