diff --git a/configure.in b/configure.in
index b41e750..07ec3e2 100644
--- a/configure.in
+++ b/configure.in
@@ -2567,8 +2567,8 @@
  getgrouplist getgroups getlogin getloadavg getpeername getpgid getpid \
  getpriority getresuid getresgid getpwent getspnam getspent getsid getwd \
  if_nameindex \
- initgroups kill killpg lchmod lchown lockf linkat lstat lutimes memrchr \
- mbrtowc mkdirat mkfifo \
+ initgroups kill killpg lchmod lchown lockf linkat lstat lutimes mmap \
+ memrchr mbrtowc mkdirat mkfifo \
  mkfifoat mknod mknodat mktime mremap nice openat pathconf pause pipe2 plock poll \
  posix_fallocate posix_fadvise pread \
  pthread_init pthread_kill putenv pwrite readlink readlinkat readv realpath renameat \
@@ -2679,15 +2679,6 @@
   [AC_MSG_RESULT(no)
 ])
 
-AC_MSG_CHECKING(whether mallopt can set malloc mmap threshold)
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-#include <malloc.h>
-]], [[mallopt(M_MMAP_THRESHOLD, 256 * 1024)]])],
-  [AC_DEFINE(HAVE_MALLOPT_MMAP_THRESHOLD, 1, Define if mallopt can set malloc mmap threshold.)
-   AC_MSG_RESULT(yes)],
-  [AC_MSG_RESULT(no)
-])
-
 AC_MSG_CHECKING(for broken unsetenv)
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
 #include <stdlib.h>