diff --git a/ChangeLog b/ChangeLog
index 2986136c77..a583d5ca74 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Jun  6 19:55:21 2010  Tanaka Akira  <akr@fsij.org>
+
+	* array.c (rb_ary_product): clear uninitialized elements in temporary
+	  array.
+
 Sun Jun  6 12:31:57 2010  Narihiro Nakamura  <authorNari@gmail.com>
 
 	* gc.c: set_heaps_increment is not
diff --git a/array.c b/array.c
index 35335f5437..04c244a385 100644
--- a/array.c
+++ b/array.c
@@ -4308,6 +4308,7 @@ rb_ary_product(int argc, VALUE *argv, VALUE ary)
     /* initialize the arrays of arrays */
     ARY_SET_LEN(t0, n);
     arrays[0] = ary;
+    for (i = 1; i < n; i++) arrays[i] = Qnil;
     for (i = 1; i < n; i++) arrays[i] = to_ary(argv[i-1]);
 
     /* initialize the counters for the arrays */