diff --git a/lib/rack/utf8_sanitizer.rb b/lib/rack/utf8_sanitizer.rb
index 6cb5c39..c5b7dd0 100644
--- a/lib/rack/utf8_sanitizer.rb
+++ b/lib/rack/utf8_sanitizer.rb
@@ -49,7 +49,7 @@ def call(env)
         input.
           force_encoding(Encoding::ASCII_8BIT).
           encode!(Encoding::UTF_8)
-        if sanitize_null_bytes && input =~ NULL_BYTE_REGEX
+        if sanitize_null_bytes && NULL_BYTE_REGEX.match?(input)
           raise NullByteInString
         end
         input