diff --git a/ChangeLog b/ChangeLog
index cd44b432e5..96352dd940 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu May 22 06:30:10 2008  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
+
+	* array.c (flatten): fix memory leak.
+
 Thu May 22 05:45:30 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* proc.c (proc_dup): should copy safe_level from src proc
diff --git a/array.c b/array.c
index 1121b0f193..0357e728f0 100644
--- a/array.c
+++ b/array.c
@@ -3143,6 +3143,8 @@ flatten(ary, level, modified)
 	ary = rb_ary_pop(stack);
     }
 
+    st_free_table(memo);
+
     return result;
 }