diff --git a/ChangeLog b/ChangeLog
index cac483ce88..c492657b32 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jan  7 20:42:06 2004  Minero Aoki  <aamine@loveruby.net>
+
+	* lib/net/http.rb (HTTPHeader#content_length): should return nil
+	  unless header exists. [ruby-dev:22519]
+
 Wed Jan  7 14:26:05 2004  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
 
 	* ext/tk/lib/tk.rb (TkPanedWindow): use epath for embedded windows.
diff --git a/lib/net/http.rb b/lib/net/http.rb
index 90c473eaf4..90843576ba 100644
--- a/lib/net/http.rb
+++ b/lib/net/http.rb
@@ -1032,7 +1032,8 @@ module Net # :nodoc:
     # Returns an Integer object which represents the Content-Length: header field
     # or +nil+ if that field is not provided.
     def content_length
-      len = @header['content-length'].to_s.slice(/\d+/) or
+      return nil unless @header.key?('content-length')
+      len = @header['content-length'].slice(/\d+/) or
           raise HTTPHeaderSyntaxError, 'wrong Content-Length format'
       len.to_i
     end