diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index 9e398c7101a..a7cb5079095 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -1354,24 +1354,23 @@ public function escape_identifiers($item, $split = TRUE)
 			return $item;
 		}
 
-		static $preg_ec;
-
-		if (empty($preg_ec))
+		if (is_array($this->_escape_char))
 		{
-			if (is_array($this->_escape_char))
-			{
-				$preg_ec = array(
-					preg_quote($this->_escape_char[0]),
-					preg_quote($this->_escape_char[1]),
-					$this->_escape_char[0],
-					$this->_escape_char[1]
-				);
-			}
-			else
-			{
-				$preg_ec[0] = $preg_ec[1] = preg_quote($this->_escape_char);
-				$preg_ec[2] = $preg_ec[3] = $this->_escape_char;
-			}
+			$preg_ec = array(
+				preg_quote($this->_escape_char[0]),
+				preg_quote($this->_escape_char[1]),
+				$this->_escape_char[0],
+				$this->_escape_char[1]
+			);
+		}
+		else
+		{
+			$preg_ec = array(
+				preg_quote($this->_escape_char),
+				preg_quote($this->_escape_char),
+				$this->_escape_char,
+				$this->_escape_char
+			);
 		}
 
 		foreach ($this->_reserved_identifiers as $id)
@@ -1503,30 +1502,24 @@ protected function _has_operator($str)
 	 */
 	protected function _get_operator($str)
 	{
-		static $_operators;
-
-		if (empty($_operators))
-		{
-			$_les = ($this->_like_escape_str !== '')
-				? '\s+'.preg_quote(trim(sprintf($this->_like_escape_str, $this->_like_escape_chr)), '/')
-				: '';
-			$_operators = array(
-				'\s*(?:<|>|!)?=\s*',             // =, <=, >=, !=
-				'\s*<>?\s*',                     // <, <>
-				'\s*>\s*',                       // >
-				'\s+IS NULL',                    // IS NULL
-				'\s+IS NOT NULL',                // IS NOT NULL
-				'\s+EXISTS\s*\(.*\)',        // EXISTS(sql)
-				'\s+NOT EXISTS\s*\(.*\)',    // NOT EXISTS(sql)
-				'\s+BETWEEN\s+',                 // BETWEEN value AND value
-				'\s+NOT BETWEEN\s+',             // NOT BETWEEN value AND value
-				'\s+IN\s*\(.*\)',            // IN(list)
-				'\s+NOT IN\s*\(.*\)',        // NOT IN (list)
-				'\s+LIKE\s+\S.*('.$_les.')?',    // LIKE 'expr'[ ESCAPE '%s']
-				'\s+NOT LIKE\s+\S.*('.$_les.')?' // NOT LIKE 'expr'[ ESCAPE '%s']
-			);
-
-		}
+		$_les = ($this->_like_escape_str !== '')
+			? '\s+'.preg_quote(trim(sprintf($this->_like_escape_str, $this->_like_escape_chr)), '/')
+			: '';
+		$_operators = array(
+			'\s*(?:<|>|!)?=\s*',             // =, <=, >=, !=
+			'\s*<>?\s*',                     // <, <>
+			'\s*>\s*',                       // >
+			'\s+IS NULL',                    // IS NULL
+			'\s+IS NOT NULL',                // IS NOT NULL
+			'\s+EXISTS\s*\(.*\)',        // EXISTS(sql)
+			'\s+NOT EXISTS\s*\(.*\)',    // NOT EXISTS(sql)
+			'\s+BETWEEN\s+',                 // BETWEEN value AND value
+			'\s+NOT BETWEEN\s+',             // NOT BETWEEN value AND value
+			'\s+IN\s*\(.*\)',            // IN(list)
+			'\s+NOT IN\s*\(.*\)',        // NOT IN (list)
+			'\s+LIKE\s+\S.*('.$_les.')?',    // LIKE 'expr'[ ESCAPE '%s']
+			'\s+NOT LIKE\s+\S.*('.$_les.')?' // NOT LIKE 'expr'[ ESCAPE '%s']
+		);
 
 		return preg_match('/'.implode('|', $_operators).'/i', $str, $match)
 			? $match[0] : FALSE;
diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index e3a4f16caf5..ce24e7665f1 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -2803,13 +2803,8 @@ protected function _is_literal($str)
 			return TRUE;
 		}
 
-		static $_str;
-
-		if (empty($_str))
-		{
-			$_str = ($this->_escape_char !== '"')
-				? array('"', "'") : array("'");
-		}
+		$_str = ($this->_escape_char !== '"')
+			? array('"', "'") : array("'");
 
 		return in_array($str[0], $_str, TRUE);
 	}
diff --git a/tests/codeigniter/database/Driver_escape_test.php b/tests/codeigniter/database/Driver_escape_test.php
new file mode 100644
index 00000000000..35b6c3a12db
--- /dev/null
+++ b/tests/codeigniter/database/Driver_escape_test.php
@@ -0,0 +1,37 @@
+<?php
+
+class Driver_escape_test extends CI_TestCase {
+
+	public function set_up()
+	{
+		class_exists('Mock_Database_DB_Driver', TRUE);
+
+		$this->mysql = new CI_DB_mysqli_driver(array());
+		$this->postgre = new CI_DB_postgre_driver(array());
+	}
+
+	// --------------------------------------------------------------------
+
+	public function test_escape_identifiers_per_driver()
+	{
+		$this->assertSame('`table`.`col`', $this->mysql->escape_identifiers('table.col'));
+		$this->assertSame('"table"."col"', $this->postgre->escape_identifiers('table.col'));
+		$this->assertSame('`table`.`col`', $this->mysql->escape_identifiers('table.col'));
+	}
+
+	// --------------------------------------------------------------------
+
+	public function test_is_literal_per_driver()
+	{
+		$is_literal = new ReflectionMethod('CI_DB_query_builder', '_is_literal');
+		if (PHP_VERSION_ID < 80100)
+		{
+			$is_literal->setAccessible(TRUE);
+		}
+
+		$this->assertTrue($is_literal->invoke($this->mysql, '"foo"'));
+		$this->assertFalse($is_literal->invoke($this->postgre, '"foo"'));
+		$this->assertTrue($is_literal->invoke($this->mysql, '"foo"'));
+	}
+
+}