diff --git a/lrlex/src/lib/mod.rs b/lrlex/src/lib/mod.rs
index ac1b37008..9dc71ceb3 100644
--- a/lrlex/src/lib/mod.rs
+++ b/lrlex/src/lib/mod.rs
@@ -46,7 +46,7 @@ pub struct LexBuildError {
 impl Error for LexBuildError {}
 
 /// The various different possible Lex parser errors.
-#[derive(Debug, PartialEq, Eq, Clone)]
+#[derive(Debug, Clone)]
 #[non_exhaustive]
 pub enum LexErrorKind {
     PrematureEnd,
@@ -59,13 +59,37 @@ pub enum LexErrorKind {
     InvalidStartState,
     InvalidStartStateName,
     DuplicateName,
-    RegexError,
+    RegexError(regex::Error),
     InvalidGrmtoolsSectionValue,
     InvalidNumber,
     DuplicateGrmtoolsSectionValue,
     VerbatimNotSupported,
 }
 
+impl LexErrorKind {
+    fn is_same_kind(&self, other: &Self) -> bool {
+        use LexErrorKind as EK;
+        match (self, other) {
+            (EK::PrematureEnd, EK::PrematureEnd)
+            | (EK::RoutinesNotSupported, EK::RoutinesNotSupported)
+            | (EK::UnknownDeclaration, EK::UnknownDeclaration)
+            | (EK::MissingSpace, EK::MissingSpace)
+            | (EK::InvalidName, EK::InvalidName)
+            | (EK::UnknownStartState, EK::UnknownStartState)
+            | (EK::DuplicateStartState, EK::DuplicateStartState)
+            | (EK::InvalidStartState, EK::InvalidStartState)
+            | (EK::InvalidStartStateName, EK::InvalidStartStateName)
+            | (EK::DuplicateName, EK::DuplicateName)
+            | (EK::InvalidGrmtoolsSectionValue, EK::InvalidGrmtoolsSectionValue)
+            | (EK::InvalidNumber, EK::InvalidNumber)
+            | (EK::DuplicateGrmtoolsSectionValue, EK::DuplicateGrmtoolsSectionValue)
+            | (EK::RegexError(_), EK::RegexError(_))
+            | (EK::VerbatimNotSupported, EK::VerbatimNotSupported) => true,
+            _ => false,
+        }
+    }
+}
+
 impl Spanned for LexBuildError {
     fn spans(&self) -> &[Span] {
         self.spans.as_slice()
@@ -84,7 +108,7 @@ impl Spanned for LexBuildError {
             | LexErrorKind::InvalidGrmtoolsSectionValue
             | LexErrorKind::InvalidNumber
             | LexErrorKind::VerbatimNotSupported
-            | LexErrorKind::RegexError => SpansKind::Error,
+            | LexErrorKind::RegexError(_) => SpansKind::Error,
             LexErrorKind::DuplicateName
             | LexErrorKind::DuplicateStartState
             | LexErrorKind::DuplicateGrmtoolsSectionValue => SpansKind::DuplicationError,
@@ -94,7 +118,7 @@ impl Spanned for LexBuildError {
 
 impl fmt::Display for LexBuildError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let s = match self.kind {
+        let s = match &self.kind {
             LexErrorKind::VerbatimNotSupported => "Verbatim code not supported",
             LexErrorKind::PrematureEnd => "File ends prematurely",
             LexErrorKind::RoutinesNotSupported => "Routines not currently supported",
@@ -109,7 +133,7 @@ impl fmt::Display for LexBuildError {
             LexErrorKind::InvalidNumber => "Invalid number",
             LexErrorKind::DuplicateGrmtoolsSectionValue => "Duplicate grmtools section value",
             LexErrorKind::DuplicateName => "Rule name already exists",
-            LexErrorKind::RegexError => "Invalid regular expression",
+            LexErrorKind::RegexError(e) => return write!(f, "Invalid regular expression: {e}"),
         };
         write!(f, "{s}")
     }
diff --git a/lrlex/src/lib/parser.rs b/lrlex/src/lib/parser.rs
index 1c78d3e72..d2af8f8ad 100644
--- a/lrlex/src/lib/parser.rs
+++ b/lrlex/src/lib/parser.rs
@@ -125,7 +125,7 @@ fn add_duplicate_occurrence(
     dup_span: Span,
 ) {
     if !errs.iter_mut().any(|e| {
-        if e.kind == kind && e.spans[0] == orig_span {
+        if e.kind.is_same_kind(&kind) && e.spans[0] == orig_span {
             e.spans.push(dup_span);
             true
         } else {
@@ -618,7 +618,7 @@ where
                 target_state,
                 &self.lex_flags,
             )
-            .map_err(|_| self.mk_error(LexErrorKind::RegexError, i))?;
+            .map_err(|e| self.mk_error(LexErrorKind::RegexError(e), i))?;
             self.rules.push(rule);
         }
         Ok(i + line_len)
@@ -864,7 +864,7 @@ mod test {
                 .expect_err("Parsed ok while expecting error");
             assert_eq!(errs.len(), 1);
             let e = &errs[0];
-            assert_eq!(e.kind, kind);
+            assert!(e.kind.is_same_kind(&kind));
             assert_eq!(
                 e.spans()
                     .iter()
@@ -892,20 +892,22 @@ mod test {
                 }
             }
 
-            assert_eq!(
-                errs.iter()
-                    .map(|e| {
-                        (
-                            e.kind.clone(),
-                            e.spans()
-                                .iter()
-                                .map(|span| line_col!(src, span))
-                                .collect::<Vec<_>>(),
-                        )
-                    })
-                    .collect::<Vec<_>>(),
-                expected.collect::<Vec<_>>()
-            );
+            for ((ek1, es1), (ek2, es2)) in errs
+                .iter()
+                .map(|e| {
+                    (
+                        e.kind.clone(),
+                        e.spans()
+                            .iter()
+                            .map(|span| line_col!(src, span))
+                            .collect::<Vec<_>>(),
+                    )
+                })
+                .zip(expected)
+            {
+                assert!(ek1.is_same_kind(&ek2));
+                assert_eq!(es1, es2);
+            }
         }
     }