diff --git a/libiberty/configure.in b/libiberty/configure.in
index 05a9df1e975..4b51ee4384b 100644
--- a/libiberty/configure.in
+++ b/libiberty/configure.in
@@ -104,7 +104,7 @@ AC_SUBST_FILE(host_makefile_frag)
 # It's OK to check for header files.  Although the compiler may not be
 # able to link anything, it had better be able to at least compile
 # something.
-AC_CHECK_HEADERS(sys/file.h sys/param.h stdlib.h string.h)
+AC_CHECK_HEADERS(sys/file.h sys/param.h stdlib.h string.h unistd.h)
 
 # This is the list of functions which libiberty will provide if they
 # are not available on the host.