diff --git a/src/Attribute/Obj/Index.php b/src/Attribute/Obj/Index.php
index 4cd773f..243d5bd 100644
--- a/src/Attribute/Obj/Index.php
+++ b/src/Attribute/Obj/Index.php
@@ -11,4 +11,4 @@ class Index {
         public IndexTypeEnum $type = IndexTypeEnum::Unique,
         public null|string $name = null,
     ) {}
-}
+}
\ No newline at end of file
diff --git a/src/Common/EntityResolver.php b/src/Common/EntityResolver.php
index f61a7b6..2decb16 100644
--- a/src/Common/EntityResolver.php
+++ b/src/Common/EntityResolver.php
@@ -5,6 +5,7 @@ namespace Ulmus\Common;
 use Notes\Common\ReflectedClass;
 use Notes\Common\ReflectedProperty;
 use Psr\SimpleCache\CacheInterface;
+use Ulmus\Attribute\Obj\Index;
 use Ulmus\Ulmus,
     Ulmus\Attribute\Obj\Table,
     Ulmus\Attribute\Obj\AdapterAttributeInterface,
@@ -214,9 +215,9 @@ class EntityResolver {
         return null;
     }
     
-    public function getCompoundKeyFields() : ? array
+    public function getCompoundKeyFields() : ? Index
     {
-        return null;
+        return $this->getAttributeImplementing(Index::class);
     }
     
     public function getUniqueFields() : ? array
diff --git a/src/EntityTrait.php b/src/EntityTrait.php
index 70b6b84..4503287 100644
--- a/src/EntityTrait.php
+++ b/src/EntityTrait.php
@@ -144,13 +144,27 @@ trait EntityTrait {
             return false;
         }
 
-        if ( null === $pkField = $this->resolveEntity()->getPrimaryKeyField($this) ) {
-            throw new Exception\EntityPrimaryKeyUnknown(sprintf("Entity %s has no field containing attributes 'primary_key'", static::class));
+        if ( null === $pkField = $this->resolveEntity()->getPrimaryKeyField() ) {
+            if ( null !== $compoundKeyFields = $this->resolveEntity()->getCompoundKeyFields() ) {
+                $loaded = false;
+
+                foreach ($compoundKeyFields->column as $column) {
+                    $field = $this->resolveEntity()->field($column);
+
+                    if (! $field->allowsNull() ) {
+                        $loaded |= isset($this->{$field->name});
+                    }
+                }
+
+                return $loaded;
+            };
+        }
+        else {
+            $key = key($pkField);
+            return isset($this->$key);
         }
 
-        $key = key($pkField);
-
-        return isset($this->$key);
+        throw new Exception\EntityPrimaryKeyUnknown(sprintf("Entity %s has no field containing attributes 'primary_key'", static::class));
     }
 
     #[Ignore]
diff --git a/src/Repository.php b/src/Repository.php
index 30e5a97..1db7f43 100644
--- a/src/Repository.php
+++ b/src/Repository.php
@@ -97,7 +97,7 @@ class Repository implements RepositoryInterface
         else {
             $pk = Ulmus::resolveEntity($this->entityClass)->getPrimaryKeyField();
 
-            if (count($pk) === 1) {
+            if ($pk && count($pk) === 1) {
                 $field = key($pk);
 
                 $this->select(Common\Sql::function('COUNT', Common\Sql::raw("DISTINCT " . $this->entityClass::field($field))));