diff --git a/crypto/openssh/session.c b/crypto/openssh/session.c
index 3f628da77384..dde75920e79c 100644
--- a/crypto/openssh/session.c
+++ b/crypto/openssh/session.c
@@ -143,7 +143,7 @@ extern int startup_pipe;
 extern void destroy_sensitive_data(void);
 extern struct sshbuf *loginmsg;
 extern struct sshauthopt *auth_opts;
-char *tun_fwd_ifnames; /* serverloop.c */
+extern char *tun_fwd_ifnames; /* serverloop.c */
 
 /* original command from peer. */
 const char *original_command = NULL;