diff --git a/src/Database/Dialect/TupleComparisonTranslatorTrait.php b/src/Database/Dialect/TupleComparisonTranslatorTrait.php
index 96fdd8133bf..23ee53fa320 100644
--- a/src/Database/Dialect/TupleComparisonTranslatorTrait.php
+++ b/src/Database/Dialect/TupleComparisonTranslatorTrait.php
@@ -79,7 +79,7 @@ protected function _transformTupleComparison(TupleComparison $expression, $query
 
         foreach ($value as $tuple) {
             $surrogate->orWhere(function ($exp) use ($fields, $tuple) {
-                foreach ($tuple as $i => $value) {
+                foreach (array_values($tuple) as $i => $value) {
                     $exp->add([$fields[$i] => $value]);
                 }
                 return $exp;
diff --git a/src/ORM/Table.php b/src/ORM/Table.php
index d99aac11792..2eff91cf7ca 100644
--- a/src/ORM/Table.php
+++ b/src/ORM/Table.php
@@ -2202,7 +2202,16 @@ public function loadInto($objects, array $contain)
         $query = $this
             ->find()
             ->where(function ($exp) use ($primaryKey, $keys) {
-                return $exp->in($this->aliasField($this->primaryKey()), $keys->toList());
+                if (is_array($primaryKey) && count($primaryKey) === 1) {
+                    $primaryKey = current($primaryKey);
+                }
+
+                if (is_string($primaryKey)) {
+                    return $exp->in($this->aliasField($primaryKey), $keys->toList());
+                }
+
+                $primaryKey = array_map([$this, 'aliasField'], $primaryKey);
+                return new \Cake\Database\Expression\TupleComparison($primaryKey, $keys->toList());
             })
             ->contain($contain);
 
@@ -2216,8 +2225,13 @@ public function loadInto($objects, array $contain)
             ->toArray();
 
         $contain = $query->contain();
-        $results = $query->indexBy($primaryKey)->toArray();
         $primaryKey = (array)$primaryKey;
+        $results = $query
+            ->indexBy(function ($e) use ($primaryKey) {
+                return implode(';', $e->extract($primaryKey));
+            })
+            ->toArray();
+
         $objects = $objects
             ->map(function ($object) use ($results, $contain, $properties, $primaryKey) {
                 $key = implode(';', $object->extract($primaryKey));
diff --git a/tests/TestCase/ORM/CompositeKeysTest.php b/tests/TestCase/ORM/CompositeKeysTest.php
index e5d123b7d79..da846b37f29 100644
--- a/tests/TestCase/ORM/CompositeKeysTest.php
+++ b/tests/TestCase/ORM/CompositeKeysTest.php
@@ -672,6 +672,52 @@ public function testFindThreadedCompositeKeys()
         $this->assertEquals($expected, $formatter($items)->toArray());
     }
 
+    /**
+     * Tets that loadInto() is capable of handling composite primary keys
+     *
+     * @return void
+     */
+    public function testLoadInto()
+    {
+        $table = TableRegistry::get('SiteAuthors');
+        $tags = TableRegistry::get('SiteTags');
+        $table->hasMany('SiteArticles', [
+            'foreignKey' => ['author_id', 'site_id'],
+        ]);
+
+        $author = $table->get([1, 1]);
+        $result = $table->loadInto($author, ['SiteArticles']);
+        $this->assertSame($author, $result);
+
+        $expected = $table->get([1, 1], ['contain' => ['SiteArticles']]);
+        $this->assertEquals($expected, $result);
+    }
+
+    /**
+     * Tets that loadInto() is capable of handling composite primary keys
+     * when loading into multiple entities
+     *
+     * @return void
+     */
+    public function testLoadIntoMany()
+    {
+        $table = TableRegistry::get('SiteAuthors');
+        $tags = TableRegistry::get('SiteTags');
+        $table->hasMany('SiteArticles', [
+            'foreignKey' => ['author_id', 'site_id'],
+        ]);
+
+        $authors = $table->find()->toList();
+        $result = $table->loadInto($authors, ['SiteArticles']);
+
+        foreach ($authors as $k => $v) {
+            $this->assertSame($result[$k], $v);
+        }
+
+        $expected = $table->find('all', ['contain' => ['SiteArticles']])->toList();
+        $this->assertEquals($expected, $result);
+    }
+
     /**
      * Helper method to skip tests when connection is SQLite.
      *