diff --git a/src/Expectations/Profanity.php b/src/Expectations/Profanity.php
index f69e9c5..8018bea 100644
--- a/src/Expectations/Profanity.php
+++ b/src/Expectations/Profanity.php
@@ -22,6 +22,6 @@ function (ObjectDescription $object) use (&$foundWords, $excluding): bool {
     },
     'to not use profanity',
     FileLineFinder::where(function (string $line) use (&$foundWords): bool {
-        return str_contains($line, (string) array_values($foundWords ?? [])[0]);
+        return str_contains(strtolower($line), strtolower(array_values($foundWords ?? [])[0]));
     })
 ));