diff --git a/lib/simple_form/form_builder.rb b/lib/simple_form/form_builder.rb
index e6b561f6..7e3b8255 100644
--- a/lib/simple_form/form_builder.rb
+++ b/lib/simple_form/form_builder.rb
@@ -183,7 +183,7 @@ module SimpleForm
       options[:as] ||= :select
       options[:collection] ||= options.fetch(:collection) {
         conditions = reflection.options[:conditions]
-        conditions = conditions.call if conditions.is_a?(Proc)
+        conditions = conditions.call if conditions.respond_to?(:call)
         reflection.klass.where(conditions).order(reflection.options[:order]).to_a
       }