diff --git a/src/SaveRelationsBehavior.php b/src/SaveRelationsBehavior.php
index d04cf1f..903db16 100644
--- a/src/SaveRelationsBehavior.php
+++ b/src/SaveRelationsBehavior.php
@@ -238,7 +238,7 @@ class SaveRelationsBehavior extends Behavior
                         if ($relation->multiple === false && !empty($model->{$relationName})) {
                             Yii::trace("Setting foreign keys for {$relationName}", __METHOD__);
                             foreach ($relation->link as $relatedAttribute => $modelAttribute) {
-                                if ($model->{$modelAttribute} !== $model->{$relationName}->{$relatedAttribute}) {
+                                if ($model->{$modelAttribute} !== $model->{$relationName}->{$relatedAttribute} && !in_array($modelAttribute, $model->primaryKey())) {
                                     $model->{$modelAttribute} = $model->{$relationName}->{$relatedAttribute};
                                 }
                             }
diff --git a/tests/SaveRelationsBehaviorTest.php b/tests/SaveRelationsBehaviorTest.php
index ee86de2..e890a23 100644
--- a/tests/SaveRelationsBehaviorTest.php
+++ b/tests/SaveRelationsBehaviorTest.php
@@ -4,7 +4,6 @@ namespace tests;
 
 
 use lhs\Yii2SaveRelationsBehavior\SaveRelationsBehavior;
-use RuntimeException;
 use tests\models\Company;
 use tests\models\DummyModel;
 use tests\models\DummyModelParent;
@@ -32,6 +31,7 @@ class SaveRelationsBehaviorTest extends \PHPUnit_Framework_TestCase
         $db->createCommand()->dropTable('project_user')->execute();
         $db->createCommand()->dropTable('project')->execute();
         $db->createCommand()->dropTable('user')->execute();
+        $db->createCommand()->dropTable('user_profile')->execute();
         $db->createCommand()->dropTable('company')->execute();
         $db->createCommand()->dropTable('link_type')->execute();
         $db->createCommand()->dropTable('link')->execute();
@@ -62,6 +62,12 @@ class SaveRelationsBehaviorTest extends \PHPUnit_Framework_TestCase
             'username' => $migration->string()->notNull()->unique()
         ])->execute();
 
+        // User profile
+        $db->createCommand()->createTable('user_profile', [
+            'user_id' => $migration->primaryKey(),
+            'bio'     => $migration->text(),
+        ])->execute();
+
         // Project
         $db->createCommand()->createTable('project', [
             'id'         => $migration->primaryKey(),
@@ -148,20 +154,25 @@ class SaveRelationsBehaviorTest extends \PHPUnit_Framework_TestCase
         ])->execute();
     }
 
-    /**
-     * @expectedException RuntimeException
-     */
     public function testCannotAttachBehaviorToAnythingButActiveRecord()
     {
+        $this->setExpectedException('RuntimeException');
         $model = new Model();
         $model->attachBehavior('saveRelated', SaveRelationsBehavior::className());
     }
 
-    /**
-     * @expectedException \yii\base\InvalidCallException
-     */
+    public function testUnsupportedRelationProperty()
+    {
+        $this->setExpectedException('\yii\base\UnknownPropertyException');
+        $model = new Project();
+        $model->detachBehaviors();
+        $model->attachBehavior('saveRelated', new SaveRelationsBehavior(['relations' => ['links' => ['fakeParam' => 'Some value']]]));
+    }
+
+
     public function testTryToSetUndeclaredRelationShouldFail()
     {
+        $this->setExpectedException('\yii\base\InvalidCallException');
         $project = new Project();
         $project->projectUsers = [];
     }
@@ -582,7 +593,7 @@ class SaveRelationsBehaviorTest extends \PHPUnit_Framework_TestCase
         $project->loadRelations($data);
         $this->assertFalse($project->save(), 'Project could be saved');
         $data = [
-            'Link'    => [
+            'Link' => [
                 [
                     'language' => 'en',
                     'name'     => 'yii',
@@ -594,4 +605,16 @@ class SaveRelationsBehaviorTest extends \PHPUnit_Framework_TestCase
         $this->assertTrue($project->save(), 'Project could not be saved');
     }
 
+    public function testSaveHasOneWithPrimaryKeyAsForeignKey()
+    {
+        $user = new User();
+        $user->username = 'Dummy More';
+        $user->userProfile = [
+            'bio' => "Some great bio"
+        ];
+        $this->assertTrue($user->save(), 'User could not be saved');
+        $this->assertEquals($user->userProfile->bio, "Some great bio");
+        $this->assertEquals($user->id, $user->userProfile->user_id);
+    }
+
 }
diff --git a/tests/models/BadConfigurationModel.php b/tests/models/BadConfigurationModel.php
new file mode 100644
index 0000000..127b11b
--- /dev/null
+++ b/tests/models/BadConfigurationModel.php
@@ -0,0 +1,48 @@
+<?php
+/**
+ * @link http://www.lahautesociete.com
+ * @copyright Copyright (c) 2016 La Haute Société
+ */
+
+namespace tests\models;
+
+use lhs\Yii2SaveRelationsBehavior\SaveRelationsBehavior;
+
+/**
+ * DummyModel class
+ *
+ * @author albanjubert
+ **/
+class BadConfigurationModel extends \yii\db\ActiveRecord
+{
+
+    /**
+     * @inheritdoc
+     */
+    public static function tableName()
+    {
+        return 'dummy';
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function behaviors()
+    {
+        return [
+            'saveRelations' => [
+                'class'     => SaveRelationsBehavior::className(),
+                'relations' => ['children']
+            ],
+        ];
+    }
+
+    /**
+     * @return \yii\db\ActiveQuery
+     */
+    public function getChildren()
+    {
+        return $this->hasOne(DummyModel::className(), ['id' => 'parent_id']);
+    }
+
+}
\ No newline at end of file
diff --git a/tests/models/User.php b/tests/models/User.php
index fdff1a6..0f7c176 100644
--- a/tests/models/User.php
+++ b/tests/models/User.php
@@ -2,6 +2,8 @@
 
 namespace tests\models;
 
+use lhs\Yii2SaveRelationsBehavior\SaveRelationsBehavior;
+
 class User extends \yii\db\ActiveRecord
 {
     /**
@@ -15,6 +17,19 @@ class User extends \yii\db\ActiveRecord
     /**
      * @inheritdoc
      */
+    public function behaviors()
+    {
+        return [
+            'saveRelations' => [
+                'class'     => SaveRelationsBehavior::className(),
+                'relations' => ['userProfile']
+            ],
+        ];
+    }
+
+    /**
+     * @inheritdoc
+     */
     public function rules()
     {
         return [
@@ -23,4 +38,12 @@ class User extends \yii\db\ActiveRecord
         ];
     }
 
+    /**
+     * @return \yii\db\ActiveQuery
+     */
+    public function getUserProfile()
+    {
+        return $this->hasOne(UserProfile::className(), ['user_id' => 'id']);
+    }
+
 }
diff --git a/tests/models/UserProfile.php b/tests/models/UserProfile.php
new file mode 100644
index 0000000..5d9c6d6
--- /dev/null
+++ b/tests/models/UserProfile.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace tests\models;
+
+class UserProfile extends \yii\db\ActiveRecord
+{
+    /**
+     * @inheritdoc
+     */
+    public static function tableName()
+    {
+        return 'user_profile';
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function rules()
+    {
+        return [
+            ['bio', 'required']
+        ];
+    }
+
+}