diff --git a/src/ORM/EntityValidator.php b/src/ORM/EntityValidator.php
index b427f7d2dbf..6601807c7ea 100644
--- a/src/ORM/EntityValidator.php
+++ b/src/ORM/EntityValidator.php
@@ -93,7 +93,8 @@ public function one(Entity $entity, $options = []) {
 			}
 
 			$validator = $association->target()->entityValidator();
-			if ($association->type() === Association::ONE_TO_ONE) {
+			$types = [Association::ONE_TO_ONE, Association::MANY_TO_ONE];
+			if (in_array($association->type(), $types)) {
 				$valid = $validator->one($value, $assoc['options']) && $valid;
 			} else {
 				$valid = $validator->many($value, $assoc['options']) && $valid;
diff --git a/src/ORM/Marshaller.php b/src/ORM/Marshaller.php
index 0f06a80b260..bfd29d82161 100644
--- a/src/ORM/Marshaller.php
+++ b/src/ORM/Marshaller.php
@@ -132,7 +132,8 @@ public function one(array $data, $include = []) {
 	protected function _marshalAssociation($assoc, $value, $include) {
 		$targetTable = $assoc->target();
 		$marshaller = $targetTable->marshaller();
-		if ($assoc->type() === Association::ONE_TO_ONE) {
+		$types = [Association::ONE_TO_ONE, Association::MANY_TO_ONE];
+		if (in_array($assoc->type(), $types)) {
 			return $marshaller->one($value, (array)$include);
 		}
 		if ($assoc->type() === Association::MANY_TO_MANY) {
@@ -327,7 +328,8 @@ protected function _mergeAssociation($original, $assoc, $value, $include) {
 
 		$targetTable = $assoc->target();
 		$marshaller = $targetTable->marshaller();
-		if ($assoc->type() === Association::ONE_TO_ONE) {
+		$types = [Association::ONE_TO_ONE, Association::MANY_TO_ONE];
+		if (in_array($assoc->type(), $types)) {
 			return $marshaller->merge($original, $value, (array)$include);
 		}
 		if ($assoc->type() === Association::MANY_TO_MANY) {
diff --git a/tests/TestCase/ORM/AssociationTest.php b/tests/TestCase/ORM/AssociationTest.php
index 6804d84753e..b32588b4918 100644
--- a/tests/TestCase/ORM/AssociationTest.php
+++ b/tests/TestCase/ORM/AssociationTest.php
@@ -52,7 +52,7 @@ public function setUp() {
 			'\Cake\ORM\Association',
 			[
 				'_options', 'attachTo', '_joinCondition', 'cascadeDelete', 'isOwningSide',
-				'save', 'eagerLoader'
+				'save', 'eagerLoader', 'type'
 			],
 			['Foo', $config]
 		);