diff --git a/ChangeLog b/ChangeLog
index 600443a1c5..7082ba044e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Fri Apr  2 14:12:24 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/rdoc/parser.rb (RDoc::Parser.binary?): blksize may be nil
+	  and is irrelevant to whether a file is binary.  TAB and newlines
+	  would be usually considered to be included in text data.
+	  reapplied r23071 and r24297.
+
 Fri Apr  2 13:59:17 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/rdoc/ri/paths.rb (RDoc::RI::Paths): Gem::Enable has been
diff --git a/lib/rdoc/parser.rb b/lib/rdoc/parser.rb
index e1b264bffa..a5c7de663f 100644
--- a/lib/rdoc/parser.rb
+++ b/lib/rdoc/parser.rb
@@ -67,7 +67,7 @@ class RDoc::Parser
   # content that an RDoc parser shouldn't try to consume.
 
   def self.binary?(file)
-    s = File.read(file, File.stat(file).blksize || 1024) || ""
+    s = File.read(file, 1024) or return false
 
     if s[0, 2] == Marshal.dump('')[0, 2] then
       true
@@ -76,10 +76,7 @@ class RDoc::Parser
     elsif s.scan(/<%|%>/).length >= 4 then
       true
     else
-      # From ptools under the Artistic License 2.0, (c) Daniel Berger.
-      s = s.split(//)
-
-      ((s.size - s.grep(" ".."~").size) / s.size.to_f) > 0.30
+      s.count("^ -~\t\r\n").fdiv(s.size) > 0.3 || s.index("\x00")
     end
   end