diff --git a/lisp/subr.el b/lisp/subr.el
index 164ed2a6f63..fa0ab09b0e7 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -4772,6 +4772,7 @@ Interactively, prompt for SOURCE.
 The replacement is performed using `replace-region-contents'
 which also describes the MAX-SECS and MAX-COSTS arguments and the
 return value."
+  (declare (obsolete replace-region-contents "31.1"))
   (interactive "bSource buffer: ")
   (replace-region-contents (point-min) (point-max) (get-buffer source)
                            max-secs max-costs))
diff --git a/src/editfns.c b/src/editfns.c
index 669d3cdb140..969b1205db2 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -1916,7 +1916,10 @@ static bool compareseq_early_abort (struct context *);
 #include "diffseq.h"
 
 DEFUN ("replace-region-contents", Freplace_region_contents,
-       Sreplace_region_contents, 3, 6, 0,
+       Sreplace_region_contents, 3, 6,
+       "(list (if (use-region-p) (region-beginning) (point-min)) \
+              (if (use-region-p) (region-end) (point-max)) 	 \
+              (get-buffer (read-buffer-to-switch \"Source buffer: \")))",
        doc: /* Replace the region between BEG and END with that of SOURCE.
 SOURCE can be a buffer, a string, or a vector [SBUF SBEG SEND]
 denoting the subtring SBEG..SEND of buffer SBUF.