diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index 293419e..7f33347 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -807,7 +807,10 @@
 			$where_in = array_values($values);
 		}
 
-		$prefix = (count($this->qb_where) === 0) ? $this->_group_get_type('') : $this->_group_get_type($type);
+		$prefix = (count($this->qb_where) === 0 && count($this->qb_cache_where) === 0)
+			? $this->_group_get_type('')
+			: $this->_group_get_type($type);
+
 		$where_in = array(
 			'condition' => $prefix.$key.$not.' IN('.implode(', ', $where_in).')',
 			'escape' => $escape
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 5d1a3ab..e409cc6 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -74,6 +74,7 @@
 -  Fixed a bug (#4000) - :doc:`Pagination Library <libraries/pagination>` didn't enable "rel" attributes by default if no attributes-related config options were used.
 -  Fixed a bug (#4004) - :doc:`URI Class <libraries/uri>` didn't properly parse the request URI if it contains a colon followed by a digit.
 -  Fixed a bug in :doc:`Query Builder <database/query_builder>` where the ``$escape`` parameter for some methods only affected field names.
+-  Fixed a bug (#4012) - :doc:`Query Builder <database/query_builder>` methods ``where_in()``, ``or_where_in()``, ``where_not_in()``, ``or_where_not_in()`` didn't take into account previously cached WHERE conditions when query cache is in use.
 
 Version 3.0.0
 =============