diff --git a/ChangeLog b/ChangeLog
index cb89ce57b3..037f862aec 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Tue Dec 25 15:24:57 2007  Tanaka Akira  <akr@fsij.org>
+
+	* io.c (appendline): initialize rslen to 1 if rsptr is 0.
+	  rslen is the length of the delimiter.
+	  if only delim is given, it should be 1.
+	  [ruby-dev:32746]
+
 Tue Dec 25 15:21:33 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* transcode.c (transcode_dispatch): fix for multistep transcode.
diff --git a/io.c b/io.c
index 4b392b8d27..9556b98ff6 100644
--- a/io.c
+++ b/io.c
@@ -1672,6 +1672,9 @@ appendline(rb_io_t *fptr, int delim, const char *rsptr, int rslen, VALUE rs, VAL
     long limit = *lp;
     rb_encoding *enc = io_input_encoding(fptr);
 
+    if (rsptr == 0)
+      rslen = 1;
+
     do {
 	long pending = READ_DATA_PENDING_COUNT(fptr);
 	if (pending > 0) {