diff --git a/bootstrap.conf b/bootstrap.conf
index 94af05134c..d029253d3a 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -42,6 +42,7 @@ fcntl
 fcntl-h
 ffs
 fnmatch
+fsync
 func
 getaddrinfo
 getcwd-lgpl
@@ -57,6 +58,7 @@ ignore-value
 inet_pton
 intprops
 ioctl
+largefile
 listen
 maintainer-makefile
 manywarnings
diff --git a/configure.ac b/configure.ac
index 0c6d524844..ad9d7541c6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -135,9 +135,12 @@ AC_CHECK_SIZEOF([long])
 
 dnl Availability of various common functions (non-fatal if missing),
 dnl and various less common threadsafe functions
-AC_CHECK_FUNCS_ONCE([cfmakeraw geteuid getgid getgrnam_r getmntent_r \
+AC_CHECK_FUNCS_ONCE([cfmakeraw fdatasync geteuid getgid getgrnam_r getmntent_r \
   getpwuid_r getuid initgroups kill mmap posix_fallocate posix_memalign \
   regexec sched_getaffinity])
+if test $ac_cv_func_fdatasync = no; then
+  AC_DEFINE([fdatasync], [fsync], [Define to fsync if you lack fdatasync])
+fi
 
 dnl Availability of pthread functions (if missing, win32 threading is
 dnl assumed).  Because of $LIB_PTHREAD, we cannot use AC_CHECK_FUNCS_ONCE.