diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 32a83259e3..6b6aca8227 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -4,6 +4,7 @@ Yii Framework 2 Change Log
 2.0.8 under development
 -----------------------
 
+- Bug #6173: Added property `yii\web\DbSession::encodeData` to encode/decode session data in base64 on session read/write (silverfire)
 - Bug #9851: Fixed partial commit / rollback in nested transactions (sammousa)
 - Bug #10946: Fixed parameters binding to the SQL query in `yii\db\mysqlSchema::findConstraints()` (silverfire)
 - Enh #5469: Add mimetype validation by mask in FileValidator (kirsenn, samdark, silverfire)
diff --git a/framework/web/DbSession.php b/framework/web/DbSession.php
index 108e94ba19..fd8e110d3d 100644
--- a/framework/web/DbSession.php
+++ b/framework/web/DbSession.php
@@ -73,7 +73,12 @@ class DbSession extends MultiFieldSession
      * length 64 instead of 40.
      */
     public $sessionTable = '{{%session}}';
-
+    /**
+     * @var boolean whether to encode the session data to base64. Defaults to false.
+     * The parameter can be useful for PgSQL DBMS where serialised session
+     * @since 2.0.8
+     */
+    public $encodeData = false;
 
     /**
      * Initializes the DbSession component.
@@ -145,7 +150,7 @@ class DbSession extends MultiFieldSession
         }
 
         $data = $query->select(['data'])->scalar($this->db);
-        return $data === false ? '' : $data;
+        return $data === false ? '' : $this->encodeData ? base64_decode($data) : $data;
     }
 
     /**
@@ -166,6 +171,7 @@ class DbSession extends MultiFieldSession
                 ->where(['id' => $id])
                 ->createCommand($this->db)
                 ->queryScalar();
+            $data = $this->encodeData ? base64_encode($data) : $data;
             $fields = $this->composeFields($id, $data);
             if ($exists === false) {
                 $this->db->createCommand()
diff --git a/tests/framework/web/DbSessionTest.php b/tests/framework/web/DbSessionTest.php
index 8e6057df97..38b63349f7 100644
--- a/tests/framework/web/DbSessionTest.php
+++ b/tests/framework/web/DbSessionTest.php
@@ -3,6 +3,7 @@
 namespace yiiunit\framework\web;
 
 use Yii;
+use yii\db\ActiveQuery;
 use yii\db\Connection;
 use yii\db\Query;
 use yii\web\DbSession;
@@ -41,6 +42,21 @@ class DbSessionTest extends TestCase
         $this->assertEquals('', $session->readSession('test'));
     }
 
+    public function testEncodeDataRW()
+    {
+        $session = new DbSession(['encodeData' => true]);
+
+        $session->writeSession('test', 'session data');
+        $session->id;
+
+        $data = (new Query())->select(['data'])->from('session')->where(['id' => 'test'])->scalar();
+        $this->assertNotRegExp('~[^0-9a-zA-Z+/=]~', $data, 'The session data contains non-base64 characters');
+
+        $this->assertEquals('session data', $session->readSession('test'));
+        $session->destroySession('test');
+        $this->assertEquals('', $session->readSession('test'));
+    }
+
     /**
      * @depends testReadWrite
      */
@@ -82,4 +98,4 @@ class DbSessionTest extends TestCase
         $this->assertEquals('session data', $sessionRow['data']);
         $this->assertEquals(15, $sessionRow['user_id']);
     }
-}
\ No newline at end of file
+}