diff --git a/src/error.rs b/src/error.rs
index 7a291ea..26edba4 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -18,6 +18,9 @@ pub enum Error {
     /// No rule for label
     #[error("No rule for label {0}")]
     NoRuleFoundForLabel(String),
+    /// Rule not found for ID
+    #[error("No rule for id {0}")]
+    RuleNotFound(usize),
     /// Label not found in the rule set
     #[error("Label `{0}` not found in the rule set")]
     LabelNotFoundInRules(String),