diff --git a/ChangeLog b/ChangeLog
index fecf7d5abc..a02c464249 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Jul 24 10:37:04 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (rb_f_p): return nil if no argument.  [ruby-dev:31285]
+
 Tue Jul 24 01:05:07 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* regint.h (USE_MATCH_RANGE_IS_COMPLETE_RANGE): undef to achieve old
diff --git a/io.c b/io.c
index cda216789b..b108b20705 100644
--- a/io.c
+++ b/io.c
@@ -3991,7 +3991,7 @@ rb_f_p(int argc, VALUE *argv, VALUE self)
     if (argc == 1) {
 	ret = argv[0];
     }
-    else {
+    else if (argc > 1) {
 	ret = rb_ary_new4(argc, argv);
     }
     if (TYPE(rb_stdout) == T_FILE) {