diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index d6f35e0..6bf039e 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -531,39 +531,47 @@
 
 		is_bool($escape) OR $escape = $this->_protect_identifiers;
 
-		// Split multiple conditions
-		if ($escape === TRUE && preg_match_all('/\sAND\s|\sOR\s/i', $cond, $m, PREG_OFFSET_CAPTURE))
-		{
-			$newcond = '';
-			$m[0][] = array('', strlen($cond));
-
-			for ($i = 0, $c = count($m[0]), $s = 0;
-				$i < $c;
-				$s = $m[0][$i][1] + strlen($m[0][$i][0]), $i++)
-			{
-				$temp = substr($cond, $s, ($m[0][$i][1] - $s));
-				$newcond .= preg_match("/(\(*)?([\[\]\w\.'-]+)(\s*[^\"\[`'\w]+\s*)(.+)/i", $temp, $match)
-						? $match[1].$this->protect_identifiers($match[2]).$match[3].$this->protect_identifiers($match[4])
-						: $temp;
-
-				$newcond .= $m[0][$i][0];
-			}
-
-			$cond = ' ON '.$newcond;
-		}
-		// Split apart the condition and protect the identifiers
-		elseif ($escape === TRUE && preg_match("/(\(*)?([\[\]\w\.'-]+)(\s*[^\"\[`'\w]+\s*)(.+)/i", $cond, $match))
-		{
-			$cond = ' ON '.$match[1].$this->protect_identifiers($match[2]).$match[3].$this->protect_identifiers($match[4]);
-		}
-		elseif ( ! $this->_has_operator($cond))
+		if ( ! $this->_has_operator($cond))
 		{
 			$cond = ' USING ('.($escape ? $this->escape_identifiers($cond) : $cond).')';
 		}
-		else
+		elseif ($escape === FALSE)
 		{
 			$cond = ' ON '.$cond;
 		}
+		else
+		{
+			// Split multiple conditions
+			if (preg_match_all('/\sAND\s|\sOR\s/i', $cond, $joints, PREG_OFFSET_CAPTURE))
+			{
+				$conditions = array();
+				$joints = $joints[0];
+				array_unshift($joints, array('', 0));
+
+				for ($i = count($joints) - 1, $pos = strlen($cond); $i >= 0; $i--)
+				{
+					$joints[$i][1] += strlen($joints[$i][0]); // offset
+					$conditions[$i] = substr($cond, $joints[$i][1], $pos - $joints[$i][1]);
+					$pos = $joints[$i][1] - strlen($joints[$i][0]);
+					$joints[$i] = $joints[$i][0];
+				}
+			}
+			else
+			{
+				$conditions = array($cond);
+				$joints = array('');
+			}
+
+			$cond = ' ON ';
+			for ($i = 0, $c = count($conditions); $i < $c; $i++)
+			{
+				$operator = $this->_get_operator($conditions[$i]);
+				$cond .= $joints[$i];
+				$cond .= preg_match("/(\(*)?([\[\]\w\.'-]+)".preg_quote($operator)."(.*)/i", $conditions[$i], $match)
+					? $match[1].$this->protect_identifiers($match[2]).$operator.$this->protect_identifiers($match[3])
+					: $conditions[$i];
+			}
+		}
 
 		// Do we want to escape the table name?
 		if ($escape === TRUE)
diff --git a/tests/codeigniter/database/query_builder/join_test.php b/tests/codeigniter/database/query_builder/join_test.php
index 58cb214..54b2a4e 100644
--- a/tests/codeigniter/database/query_builder/join_test.php
+++ b/tests/codeigniter/database/query_builder/join_test.php
@@ -37,6 +37,29 @@
 
 	// ------------------------------------------------------------------------
 
+	public function test_join_escape_is_null()
+	{
+		$expected = 'SELECT '.$this->db->escape_identifiers('field')
+				."\nFROM ".$this->db->escape_identifiers('table1')
+				."\nJOIN ".$this->db->escape_identifiers('table2').' ON '.$this->db->escape_identifiers('field').' IS NULL';
+
+		$this->assertEquals(
+			$expected,
+			$this->db->select('field')->from('table1')->join('table2', 'field IS NULL')->get_compiled_select()
+		);
+
+		$expected = 'SELECT '.$this->db->escape_identifiers('field')
+				."\nFROM ".$this->db->escape_identifiers('table1')
+				."\nJOIN ".$this->db->escape_identifiers('table2').' ON '.$this->db->escape_identifiers('field').' IS NOT NULL';
+
+		$this->assertEquals(
+			$expected,
+			$this->db->select('field')->from('table1')->join('table2', 'field IS NOT NULL')->get_compiled_select()
+		);
+	}
+
+	// ------------------------------------------------------------------------
+
 	public function test_join_escape_multiple_conditions()
 	{
 		// We just need a valid query produced, not one that makes sense
@@ -65,11 +88,11 @@
 		$expected = 'SELECT '.implode(', ', $fields)
 				."\nFROM ".$this->db->escape_identifiers('table1')
 				."\nRIGHT JOIN ".$this->db->escape_identifiers('table2').' ON '.implode(' = ', $fields)
-				.' AND ('.$fields[0]." = 'foo' OR ".$fields[1].' = 0)';
+				.' AND ('.$fields[0]." = 'foo' OR ".$fields[1].' IS NULL)';
 
 		$result = $this->db->select('table1.field1, table2.field2')
 				->from('table1')
-				->join('table2', "table1.field1 = table2.field2 AND (table1.field1 = 'foo' OR table2.field2 = 0)", 'RIGHT')
+				->join('table2', "table1.field1 = table2.field2 AND (table1.field1 = 'foo' OR table2.field2 IS NULL)", 'RIGHT')
 				->get_compiled_select();
 
 		$this->assertEquals($expected, $result);