diff --git a/CHANGELOG-Japanese.md b/CHANGELOG-Japanese.md
index 0c211e9e..9b4bcde4 100644
--- a/CHANGELOG-Japanese.md
+++ b/CHANGELOG-Japanese.md
@@ -21,6 +21,7 @@
 **バグ修正:**
 
 - `--start-timeline`、`--end-timeline`オプションが動かなかったのを修正した。 (#546) (@hitenkoku)
+- ルール内の`level`が正しくない場合に検知数が最も多い日の集計の際にcrashが起きるのを修正した。 (#560) (@hitenkoku)
 
 ## v1.2.2 [2022/05/20]
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f6e191f7..018d0b49 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,7 +21,7 @@
 **Bug Fixes:**
 
 - Fixed the `--start-timeline` and `--end-timeline` options as they were not working. (#546) @hitenkoku)
-
+- Fixed crash bug when level in rule is not valid. (#560) (@hitenkoku)
 
 ## v1.2.2 [2022/05/20]
 
diff --git a/src/afterfact.rs b/src/afterfact.rs
index 4ecb5cc2..6a271127 100644
--- a/src/afterfact.rs
+++ b/src/afterfact.rs
@@ -294,7 +294,7 @@ fn emit_csv<W: std::io::Write>(
             let time_str_date = &time_str[0..10];
             let mut detect_counts_by_date = detect_counts_by_date_and_level
                 .get(&detect_info.level.to_lowercase())
-                .unwrap()
+                .unwrap_or_else(|| detect_counts_by_date_and_level.get("undefined").unwrap())
                 .clone();
             *detect_counts_by_date
                 .entry(time_str_date.to_string())