diff -u -r1.35.2.1 nbtool_config.h.in
--- a/tools/compat/nbtool_config.h.in	22 Apr 2015 07:18:58 -0000	1.35.2.1
+++ b/tools/compat/nbtool_config.h.in	31 May 2018 01:46:53 -0000
@@ -680,5 +680,14 @@
 /* Define if you have u_int8_t, but not uint8_t. */
 #undef uint8_t
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include "compat_defs.h"
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* !__NETBSD_NBTOOL_CONFIG_H__ */