diff --git a/lib/extensions/string.dart b/lib/extensions/string.dart
index bdc275f..22ad1af 100644
--- a/lib/extensions/string.dart
+++ b/lib/extensions/string.dart
@@ -5,7 +5,7 @@ const negativeNumberPreface = 'Negative';
 extension StringExtension on String {
   String get alphanumeric {
     // Match '-' only if it is followed by a digit and replace with negativeNumberPreface
-    final patternNegative = RegExp(r'-(?=\d)');
+    final patternNegative = RegExp(r'^(-)(?=\d)');
     // Match all non alphanumeric characters (excluding negativeNumberPreface replacements) and replace them with a space
     final patternNonAlphanumeric = RegExp(r'[^a-zA-Z0-9]');
 
diff --git a/test/extensions/strings_test.dart b/test/extensions/strings_test.dart
index 0e81ee9..425c0ff 100644
--- a/test/extensions/strings_test.dart
+++ b/test/extensions/strings_test.dart
@@ -35,5 +35,18 @@ void main() {
   test('extension alphanumeric negative numbers', () {
     final test = '-4';
     expect(test.alphanumeric, 'Negative4');
+    final test2 = '-4-grey';
+    expect(test2.alphanumeric, 'Negative4Grey');
+    final test3 = '--4';
+    expect(test3.alphanumeric, '4');
+    final test4 = '-grey-4';
+    expect(test4.alphanumeric, 'Grey4');
+  });
+
+  test('extension alphanumeric with minus sign', () {
+    final test = 'White-4';
+    expect(test.alphanumeric, 'White4');
+    final test2 = 'White-4-dog';
+    expect(test2.alphanumeric, 'White4Dog');
   });
 }