[ci skip] Add a note to the user guide regarding issue #1010
diff --git a/user_guide_src/source/libraries/form_validation.rst b/user_guide_src/source/libraries/form_validation.rst
index 39f7874..faf2219 100644
--- a/user_guide_src/source/libraries/form_validation.rst
+++ b/user_guide_src/source/libraries/form_validation.rst
@@ -861,8 +861,9 @@
========================= ========== ============================================================================================= =======================
**required** No Returns FALSE if the form element is empty.
**matches** Yes Returns FALSE if the form element does not match the one in the parameter. matches[form_item]
-**is_unique** Yes Returns FALSE if the form element is not unique to the is_unique[table.field]
- table and field name in the parameter. is_unique[table.field]
+**is_unique** Yes Returns FALSE if the form element is not unique to the table and field name in the is_unique[table.field]
+ parameter. Note: This rule requires :doc:`Query Builder <database/query_builder>` to be
+ enabled in order to work.
**max_length** Yes Returns FALSE if the form element is longer then the parameter value. max_length[12]
**exact_length** Yes Returns FALSE if the form element is not exactly the parameter value. exact_length[8]
**greater_than** Yes Returns FALSE if the form element is less than or equal to the parameter value or not greater_than[8]