1 files changed, 6 insertions, 2 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/public_exceptions.rb b/actionpack/lib/action_dispatch/middleware/public_exceptions.rb
index 3feb3a19f3..a88ad40f21 100644
--- a/actionpack/lib/action_dispatch/middleware/public_exceptions.rb
+++ b/actionpack/lib/action_dispatch/middleware/public_exceptions.rb
@@ -21,8 +21,12 @@ module ActionDispatch
     def call(env)
       request      = ActionDispatch::Request.new(env)
       status       = request.path_info[1..-1].to_i
-      content_type = request.formats.first
-      body         = { status: status, error: Rack::Utils::HTTP_STATUS_CODES.fetch(status, Rack::Utils::HTTP_STATUS_CODES[500]) }
+      begin
+        content_type = request.formats.first
+      rescue Mime::Type::InvalidMimeType
+        content_type = Mime[:text]
+      end
+      body = { status: status, error: Rack::Utils::HTTP_STATUS_CODES.fetch(status, Rack::Utils::HTTP_STATUS_CODES[500]) }
 
       render(status, content_type, body)
     end