diff --git a/lib/rack/multipart/parser.rb b/lib/rack/multipart/parser.rb
index 3d4e0f9b9..995846947 100644
--- a/lib/rack/multipart/parser.rb
+++ b/lib/rack/multipart/parser.rb
@@ -7,7 +7,8 @@
 
 module Rack
   module Multipart
-    class MultipartPartLimitError < Errno::EMFILE;
+    class MultipartPartLimitError < Errno::EMFILE
+      include BadRequest
     end
 
     # Use specific error class when parsing multipart request
@@ -18,9 +19,13 @@ class EmptyContentError < ::EOFError
 
     # Base class for multipart exceptions that do not subclass from
     # other exception classes for backwards compatibility.
-    class Error < StandardError
+    class BoundaryTooLongError < StandardError
+      include BadRequest
     end
 
+    Error = BoundaryTooLongError
+    deprecate_constant :Error
+
     EOL = "\r\n"
     MULTIPART = %r|\Amultipart/.*boundary=\"?([^\";,]+)\"?|ni
     TOKEN = /[^\s()<>,;:\\"\/\[\]?=]+/
@@ -101,7 +106,7 @@ def self.parse(io, content_length, content_type, tmpfile, bufsize, qp)
         if boundary.length > 70
           # RFC 1521 Section 7.2.1 imposes a 70 character maximum for the boundary.
           # Most clients use no more than 55 characters.
-          raise Error, "multipart boundary size too large (#{boundary.length} characters)"
+          raise BoundaryTooLongError, "multipart boundary size too large (#{boundary.length} characters)"
         end
 
         io = BoundedIO.new(io, content_length) if content_length