1 files changed, 1 insertions, 1 deletions

diff --git a/configure.ac b/configure.ac
index 2fbdc538..8414a710 100644
--- a/configure.ac
+++ b/configure.ac
@@ -547,7 +547,7 @@ AC_CHECK_HEADERS([fcntl.h math.h errno.h limits.h stdio.h locale.h sys/stat.h sy
 # Check for optional headers
 AC_CHECK_HEADERS([sys/types.h sys/time.h sys/msg.h netdb.h netinet/in.h netinet/tcp.h time.h sys/socket.h sys/mman.h arpa/inet.h sys/select.h search.h \
   endian.h machine/endian.h sys/endian.h sys/param.h sys/machine.h sys/byteorder.h machine/param.h sys/isa_defs.h \
-  inttypes.h stddef.h \
+  inttypes.h stddef.h unistd.h \
   sockLib.h inetLib.h net/if.h])
 AM_CONDITIONAL([HAVE_TSEARCH], [test "x$ac_cv_header_search_h" = "xyes"])