diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index dc2c5e7..978fc6a 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -644,7 +644,7 @@
 				? $this->_group_get_type('')
 				: $this->_group_get_type($type);
 
-			if ( ! is_null($v))
+			if ($v !== NULL)
 			{
 				if ($escape === TRUE)
 				{
@@ -1202,7 +1202,7 @@
 	 */
 	public function limit($value, $offset = FALSE)
 	{
-		is_null($value) OR $this->qb_limit = (int) $value;
+		$value === NULL OR $this->qb_limit = (int) $value;
 		empty($offset) OR $this->qb_offset = (int) $offset;
 
 		return $this;
@@ -1382,7 +1382,7 @@
 			$this->from($table);
 		}
 
-		if ( ! is_null($where))
+		if ($where !== NULL)
 		{
 			$this->where($where);
 		}
@@ -1411,7 +1411,7 @@
 	 */
 	public function insert_batch($table = '', $set = NULL, $escape = NULL)
 	{
-		if ( ! is_null($set))
+		if ($set !== NULL)
 		{
 			$this->set_insert_batch($set, '', $escape);
 		}
@@ -1567,7 +1567,7 @@
 	 */
 	public function insert($table = '', $set = NULL, $escape = NULL)
 	{
-		if ( ! is_null($set))
+		if ($set !== NULL)
 		{
 			$this->set($set, '', $escape);
 		}
@@ -1633,7 +1633,7 @@
 	 */
 	public function replace($table = '', $set = NULL)
 	{
-		if ( ! is_null($set))
+		if ($set !== NULL)
 		{
 			$this->set($set);
 		}
@@ -1742,7 +1742,7 @@
 		// Combine any cached components with the current statements
 		$this->_merge_cache();
 
-		if ( ! is_null($set))
+		if ($set !== NULL)
 		{
 			$this->set($set);
 		}
@@ -1815,12 +1815,12 @@
 		// Combine any cached components with the current statements
 		$this->_merge_cache();
 
-		if (is_null($index))
+		if ($index === NULL)
 		{
 			return ($this->db_debug) ? $this->display_error('db_must_use_index') : FALSE;
 		}
 
-		if ( ! is_null($set))
+		if ($set !== NULL)
 		{
 			$this->set_update_batch($set, $index);
 		}