diff --git a/ChangeLog b/ChangeLog
index f0ec77f7e7..d097599059 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Jun 21 15:07:42 2013  Koichi Sasada  <ko1@atdot.net>
+
+	* gc.c: enable lazy sweep (commit miss).
+
 Fri Jun 21 14:31:29 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* hash.c (ruby_setenv): refine error message so include the variable
diff --git a/gc.c b/gc.c
index 659b0bac9d..a2658df072 100644
--- a/gc.c
+++ b/gc.c
@@ -148,7 +148,7 @@ void rb_gcdebug_print_obj_condition(VALUE obj);
 #define GC_PROFILE_MORE_DETAIL 0
 #endif
 #ifndef GC_ENABLE_LAZY_SWEEP
-#define GC_ENABLE_LAZY_SWEEP 0
+#define GC_ENABLE_LAZY_SWEEP   1
 #endif
 #ifndef CALC_EXACT_MALLOC_SIZE
 #define CALC_EXACT_MALLOC_SIZE 0