diff --git a/libguile/socket.c b/libguile/socket.c
index 2c3c5714b..2fa9c4114 100644
--- a/libguile/socket.c
+++ b/libguile/socket.c
@@ -27,6 +27,12 @@
 int close P ((int fd));
 #endif /* STDC_HEADERS */
 
+#ifdef __STDC__
+extern int inet_aton (const char *, struct in_addr *);
+#else
+extern int inet_aton ();
+#endif
+
 SCM_PROC (s_sys_inet_aton, "inet-aton", 1, 0, 0, scm_sys_inet_aton);
 #ifdef __STDC__
 SCM