diff --git a/modules/field/field.info.inc b/modules/field/field.info.inc
index 1c6d6cddeb0..eb5cc5ca7cf 100644
--- a/modules/field/field.info.inc
+++ b/modules/field/field.info.inc
@@ -613,7 +613,8 @@ function field_info_fields() {
  * @return
  *   The field array, as returned by field_read_fields(), with an
  *   additional element 'bundles', whose value is an array of all the bundles
- *   this field belongs to keyed by entity type.
+ *   this field belongs to keyed by entity type. NULL if the field was not
+ *   found.
  *
  * @see field_info_field_by_id()
  */