diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index 5491b20..5a86ce5 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -679,7 +679,7 @@
 				// value appears not to have been set, assign the test to IS NULL
 				$k .= ' IS NULL';
 			}
-			elseif (preg_match('/\s*(!?=|<>|IS(?:\s+NOT)?)\s*$/i', $k, $match, PREG_OFFSET_CAPTURE))
+			elseif (preg_match('/\s*(!?=|<>|\sIS(?:\s+NOT)?\s)\s*$/i', $k, $match, PREG_OFFSET_CAPTURE))
 			{
 				$k = substr($k, 0, $match[0][1]).($match[1][0] === '=' ? ' IS NULL' : ' IS NOT NULL');
 			}
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 58ca20e..0a8160a 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -20,6 +20,7 @@
 
 -  Fixed a regression (#4874) - :doc:`Session Library <libraries/sessions>` didn't take into account ``session.hash_bits_per_character`` when validating session IDs.
 -  Fixed a bug (#4871) - :doc:`Query Builder <database/query_builder>` method ``update_batch()`` didn't properly handle identifier escaping.
+-  Fixed a bug (#4884) - :doc:`Query Builder <database/query_builder>` didn't properly parse field names ending in 'is' when used inside WHERE and HAVING statements.
 
 Version 3.1.1
 =============