diff --git a/lib/sinatra/base.rb b/lib/sinatra/base.rb
index 7f182e2907..ba8693632d 100644
--- a/lib/sinatra/base.rb
+++ b/lib/sinatra/base.rb
@@ -1013,6 +1013,7 @@ def process_route(pattern, keys, conditions, block = nil, values = [])
       @env['sinatra.error.params'] = @params
       raise
     ensure
+      response['Content-Type'] = nil
       @params = original if original
     end