diff -ur bison-2.7-pristine/lib/vasnprintf.c bison-2.7/lib/vasnprintf.c
--- bison-2.7-pristine/lib/vasnprintf.c	2012-11-30 20:48:23.000000000 +0900
+++ bison-2.7/lib/vasnprintf.c	2018-06-28 16:55:31.000000000 +0900
@@ -4870,7 +4870,7 @@
 #endif
                   *fbp = dp->conversion;
 #if USE_SNPRINTF
-# if !(((__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 3)) && !defined __UCLIBC__) || ((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__))
+# if !(((__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 3)) && !defined __UCLIBC__) || ((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__) || (defined __APPLE__ && defined __MACH__))
                 fbp[1] = '%';
                 fbp[2] = 'n';
                 fbp[3] = '\0';