diff --git a/job.c b/job.c
index 31178ea6..51aa92b5 100644
--- a/job.c
+++ b/job.c
@@ -117,12 +117,14 @@ extern int geteuid (), getegid ();
 extern int setgid (), getgid ();
 #endif	/* GNU C library.  */
 
+#ifndef	getdtablesize
 #ifndef USG
 extern int getdtablesize ();
 #else
 #include <sys/param.h>
 #define getdtablesize() NOFILE
 #endif
+#endif
 
 extern void wait_to_start_job ();
 extern int start_remote_job_p ();