diff --git a/model/DataObject.php b/model/DataObject.php
index 6a0cb3cfd..c6082873f 100644
--- a/model/DataObject.php
+++ b/model/DataObject.php
@@ -1786,6 +1786,12 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 		$extraFields = $this->manyManyExtraFieldsForComponent($componentName) ?: array();
 		$result = ManyManyList::create($componentClass, $table, $componentField, $parentField, $extraFields);
 
+
+		// Store component data in query meta-data
+		$result = $result->alterDataQuery(function($query) use ($extraFields) {
+			$query->setQueryParam('Component.ExtraFields', $extraFields);
+		});
+		
 		if($this->model) $result->setDataModel($this->model);
 
 		$this->extend('updateManyManyComponents', $result);
@@ -2683,6 +2689,28 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 		return $this;
 	}
 
+	/**
+	 * {@inheritdoc}
+	 */
+	public function castingHelper($field) {
+		if ($fieldSpec = $this->db($field)) {
+			return $fieldSpec;
+		}
+
+		// many_many_extraFields aren't presented by db(), so we check if the source query params
+		// provide us with meta-data for a many_many relation we can inspect for extra fields.
+		$queryParams = $this->getSourceQueryParams();
+		if (!empty($queryParams['Component.ExtraFields'])) {
+			$extraFields = $queryParams['Component.ExtraFields'];
+
+			if (isset($extraFields[$field])) {
+				return $extraFields[$field];
+			}
+		}
+
+		return parent::castingHelper($field);
+	}
+
 	/**
 	 * Returns true if the given field exists in a database column on any of
 	 * the objects tables and optionally look up a dynamic getter with
diff --git a/tests/model/DataObjectTest.php b/tests/model/DataObjectTest.php
index 08a4bcd29..766ec7fd8 100644
--- a/tests/model/DataObjectTest.php
+++ b/tests/model/DataObjectTest.php
@@ -911,6 +911,16 @@ class DataObjectTest extends SapphireTest {
 		$this->assertEmpty($fields);
 	}
 
+	public function testCastingHelper() {
+		$team = $this->objFromFixture('DataObjectTest_Team', 'team1');
+
+		$this->assertEquals('Varchar', $team->castingHelper('Title'), 'db field wasn\'t casted correctly');
+		$this->assertEquals('HTMLVarchar', $team->castingHelper('DatabaseField'), 'db field wasn\'t casted correctly');
+
+		$sponsor = $team->Sponsors()->first();
+		$this->assertEquals('Int', $sponsor->castingHelper('SponsorFee'), 'many_many_extraFields not casted correctly');
+	}
+
 	public function testSummaryFieldsCustomLabels() {
 		$team = $this->objFromFixture('DataObjectTest_Team', 'team1');
 		$summaryFields = $team->summaryFields();