diff --git a/guc.c b/guc.c
index 3000c8b..6bab2d5 100644
--- a/guc.c
+++ b/guc.c
@@ -119,7 +119,7 @@ init_guc(void)
 	{
 		.guc_name = "pg_stat_monitor.pgsm_histogram_min",
 			.guc_desc = "Sets the time in millisecond.",
-			.guc_default = 0,
+			.guc_default = 1,
 			.guc_min = 0,
 			.guc_max = INT_MAX,
 			.guc_restart = true,
@@ -145,7 +145,7 @@ init_guc(void)
 	{
 		.guc_name = "pg_stat_monitor.pgsm_histogram_buckets",
 			.guc_desc = "Sets the maximum number of histogram buckets",
-			.guc_default = 10,
+			.guc_default = 20,
 			.guc_min = 2,
 			.guc_max = MAX_RESPONSE_BUCKET,
 			.guc_restart = true,
diff --git a/regression/expected/guc.out b/regression/expected/guc.out
index 56bdaab..3b07ada 100644
--- a/regression/expected/guc.out
+++ b/regression/expected/guc.out
@@ -17,9 +17,9 @@ SELECT * FROM pg_stat_monitor_settings WHERE name NOT LIKE 'pg_stat_monitor.pgsm
  pg_stat_monitor.pgsm_bucket_time         | 60     | 60            | Sets the time in seconds per bucket.                                                                     |       1 | 2147483647 |                | yes
  pg_stat_monitor.pgsm_enable_query_plan   | no     | no            | Enable/Disable query plan monitoring                                                                     |         |            | yes, no        | no
  pg_stat_monitor.pgsm_extract_comments    | no     | no            | Enable/Disable extracting comments from queries.                                                         |         |            | yes, no        | no
- pg_stat_monitor.pgsm_histogram_buckets   | 10     | 10            | Sets the maximum number of histogram buckets                                                             |       2 |         50 |                | yes
+ pg_stat_monitor.pgsm_histogram_buckets   | 20     | 20            | Sets the maximum number of histogram buckets                                                             |       2 |         50 |                | yes
  pg_stat_monitor.pgsm_histogram_max       | 100000 | 100000        | Sets the time in millisecond.                                                                            |      10 | 2147483647 |                | yes
- pg_stat_monitor.pgsm_histogram_min       | 0      | 0             | Sets the time in millisecond.                                                                            |       0 | 2147483647 |                | yes
+ pg_stat_monitor.pgsm_histogram_min       | 1      | 1             | Sets the time in millisecond.                                                                            |       0 | 2147483647 |                | yes
  pg_stat_monitor.pgsm_max                 | 100    | 100           | Sets the maximum size of shared memory in (MB) used for statement's metadata tracked by pg_stat_monitor. |       1 |       1000 |                | yes
  pg_stat_monitor.pgsm_max_buckets         | 10     | 10            | Sets the maximum number of buckets.                                                                      |       1 |         10 |                | yes
  pg_stat_monitor.pgsm_normalized_query    | no     | no            | Selects whether save query in normalized format.                                                         |         |            | yes, no        | no