diff --git a/lib/rollbar/middleware/rails/show_exceptions.rb b/lib/rollbar/middleware/rails/show_exceptions.rb
index 3e6e79b3..fe51029b 100644
--- a/lib/rollbar/middleware/rails/show_exceptions.rb
+++ b/lib/rollbar/middleware/rails/show_exceptions.rb
@@ -7,7 +7,7 @@ module ShowExceptions
         def render_exception_with_rollbar(env, exception, wrapper = nil)
           key = 'action_dispatch.show_detailed_exceptions'
 
-          if exception.is_a?(ActionController::RoutingError) && env[key]
+          if exception.is_a?(ActionController::RoutingError) && env.params[key.to_s]
             scope = extract_scope_from(env)
 
             Rollbar.scoped(scope) do