diff --git a/ChangeLog b/ChangeLog
index 77de182d30..b570c145f5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Sep  7 17:29:49 2008  Tanaka Akira  <akr@fsij.org>
+
+	* tool/transcode-tblgen.rb: o4 is usable only if the first byte is
+	  f0-f7.
+
 Sun Sep  7 12:44:26 2008  Tanaka Akira  <akr@fsij.org>
 
 	* io.c (make_writeconv): choose ASCII compatible encoding as
diff --git a/tool/transcode-tblgen.rb b/tool/transcode-tblgen.rb
index 2ed9f13618..6f98f10ea3 100644
--- a/tool/transcode-tblgen.rb
+++ b/tool/transcode-tblgen.rb
@@ -299,7 +299,7 @@ class ActionMap
       "o2(0x#$1,0x#$2)"
     when /\A([0-9a-f][0-9a-f])([0-9a-f][0-9a-f])([0-9a-f][0-9a-f])\z/i
       "o3(0x#$1,0x#$2,0x#$3)"
-    when /\A([0-9a-f][0-9a-f])([0-9a-f][0-9a-f])([0-9a-f][0-9a-f])([0-9a-f][0-9a-f])\z/i
+    when /\A(f[0-7])([0-9a-f][0-9a-f])([0-9a-f][0-9a-f])([0-9a-f][0-9a-f])\z/i
       "o4(0x#$1,0x#$2,0x#$3,0x#$4)"
     when /\A\/\*BYTE_LOOKUP\*\// # pointer to BYTE_LOOKUP structure
       $'.to_s