diff --git a/extensions/mongo/ActiveRecord.php b/extensions/mongo/ActiveRecord.php
index 5e2d9bc..ddbfd2a 100644
--- a/extensions/mongo/ActiveRecord.php
+++ b/extensions/mongo/ActiveRecord.php
@@ -1157,4 +1157,29 @@ abstract class ActiveRecord extends Model
 			throw new InvalidParamException(get_class($this) . ' has no relation named "' . $name . '".', 0, $e);
 		}
 	}
+
+	/**
+	 * Sets the element at the specified offset.
+	 * This method is required by the SPL interface `ArrayAccess`.
+	 * It is implicitly called when you use something like `$model[$offset] = $item;`.
+	 * @param integer $offset the offset to set element
+	 * @param mixed $item the element value
+	 * @throws \Exception on failure
+	 */
+	public function offsetSet($offset, $item)
+	{
+		// Bypass relation owner restriction to 'yii\db\ActiveRecord' at [[yii\db\ActiveRelationTrait::findWith()]]:
+		try {
+			$relation = $this->getRelation($offset);
+			if (is_object($relation)) {
+				$this->populateRelation($offset, $item);
+				return;
+			}
+		} catch (InvalidParamException $e) {
+			// shut down exception : has getter, but not relation
+		} catch (UnknownMethodException $e) {
+			throw $e->getPrevious();
+		}
+		parent::offsetSet($offset, $item);
+	}
 }
\ No newline at end of file
diff --git a/extensions/mongo/Collection.php b/extensions/mongo/Collection.php
index 7959186..17a4329 100644
--- a/extensions/mongo/Collection.php
+++ b/extensions/mongo/Collection.php
@@ -267,8 +267,18 @@ class Collection extends Object
 				$key = $this->normalizeConditionKeyword($key);
 				if (strncmp('$', $key, 1) !== 0 && is_array($actualValue) && array_key_exists(0, $actualValue)) {
 					// shortcut for IN condition
+					if ($key == '_id') {
+						foreach ($actualValue as &$actualValuePart) {
+							if (!is_object($actualValuePart)) {
+								$actualValuePart = new \MongoId($actualValuePart);
+							}
+						}
+					}
 					$result[$key]['$in'] = $actualValue;
 				} else {
+					if ($key == '_id' && !is_object($actualValue)) {
+						$actualValue = new \MongoId($actualValue);
+					}
 					$result[$key] = $actualValue;
 				}
 			}
diff --git a/tests/unit/extensions/mongo/ActiveRelationTest.php b/tests/unit/extensions/mongo/ActiveRelationTest.php
index ae12d72..26cf63e 100644
--- a/tests/unit/extensions/mongo/ActiveRelationTest.php
+++ b/tests/unit/extensions/mongo/ActiveRelationTest.php
@@ -77,7 +77,7 @@ class ActiveRelationTest extends MongoTestCase
 		$this->assertEquals(10, count($orders));
 		$this->assertTrue($orders[0]->isRelationPopulated('customer'));
 		$this->assertTrue($orders[1]->isRelationPopulated('customer'));
-		$this->assertTrue($orders[0]->index instanceof ArticleIndex);
-		$this->assertTrue($orders[1]->index instanceof ArticleIndex);
+		$this->assertTrue($orders[0]->customer instanceof Customer);
+		$this->assertTrue($orders[1]->customer instanceof Customer);
 	}
 }
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/QueryRunTest.php b/tests/unit/extensions/mongo/QueryRunTest.php
index f8821b6..078e1c7 100644
--- a/tests/unit/extensions/mongo/QueryRunTest.php
+++ b/tests/unit/extensions/mongo/QueryRunTest.php
@@ -105,4 +105,16 @@ class QueryRunTest extends MongoTestCase
 			->all($connection);
 		$this->assertEquals('name9', $rows[0]['name']);
 	}
+
+	public function testMatchPlainId()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$row = $query->from('customer')->one($connection);
+		$query = new Query;
+		$rows = $query->from('customer')
+			->where(['_id' => $row['_id']->__toString()])
+			->all($connection);
+		$this->assertEquals(1, count($rows));
+	}
 }
\ No newline at end of file