diff --git a/ChangeLog b/ChangeLog
index cc6753c145..f9f13fdf4d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Sep  2 23:38:29 2007  Tanaka Akira  <akr@fsij.org>
+
+	* include/ruby/st.h (struct st_table): make num_entries bitfield
+	  instead of num_bins for speed.  num_entries has less access.
+
 Sun Sep  2 00:37:57 2007  Tadayoshi Funaba  <tadf@dotrb.org>
 
 	* lib/date/format.rb (_parse): improved parsing of ordinal dates.
diff --git a/include/ruby/st.h b/include/ruby/st.h
index 3b64bd72fb..93089b0d3b 100644
--- a/include/ruby/st.h
+++ b/include/ruby/st.h
@@ -54,9 +54,9 @@ typedef st_data_t st_index_t;
 
 struct st_table {
     const struct st_hash_type *type;
+    st_index_t num_bins;
     unsigned int entries_packed : 1;
-    st_index_t num_bins : ST_INDEX_BITS - 1;
-    st_index_t num_entries;
+    st_index_t num_entries : ST_INDEX_BITS - 1;
     struct st_table_entry **bins;
     struct st_table_entry *head;
 };