- (djm) Sync with V_3_7 branch:
   - (djm) Fix SSH1 challenge kludge
   - (djm) Bug #671: Fix builds on OpenBSD
   - (djm) Bug #676: Fix PAM stack corruption
   - (djm) Fix bad free() in PAM code
   - (djm) Don't call pam_end before pam_init
   - (djm) Enable build with old OpenSSL again
   - (djm) Trim deprecated options from INSTALL. Mention UsePAM
   - (djm) Fix quote handling in sftp; Patch from admorten AT umich.edu
diff --git a/log.c b/log.c
index 58ce8e5..9bce255 100644
--- a/log.c
+++ b/log.c
@@ -40,6 +40,9 @@
 #include "xmalloc.h"
 
 #include <syslog.h>
+#if defined(HAVE_STRNVIS) && defined(HAVE_VIS_H)
+# include <vis.h>
+#endif
 
 static LogLevel log_level = SYSLOG_LEVEL_INFO;
 static int log_on_stderr = 1;