diff --git a/Describer/OpenApiPhpDescriber.php b/Describer/OpenApiPhpDescriber.php
index 4f03918..96aad2d 100644
--- a/Describer/OpenApiPhpDescriber.php
+++ b/Describer/OpenApiPhpDescriber.php
@@ -47,7 +47,7 @@ final class OpenApiPhpDescriber
         $classAnnotations = [];
 
         /** @var \ReflectionMethod $method */
-        foreach ($this->getMethodsToParse() as $method => list($path, $httpMethods)) {
+        foreach ($this->getMethodsToParse() as $method => list($path, $httpMethods, $routeName)) {
             $declaringClass = $method->getDeclaringClass();
 
             $path = Util::getPath($api, $path);
@@ -134,6 +134,10 @@ final class OpenApiPhpDescriber
                 $operation = Util::getOperation($path, $httpMethod);
                 $operation->merge($implicitAnnotations);
                 $operation->mergeProperties($mergeProperties);
+
+                if (OA\UNDEFINED === $operation->operationId) {
+                    $operation->operationId = $httpMethod.'_'.$routeName;
+                }
             }
         }
 
@@ -143,7 +147,7 @@ final class OpenApiPhpDescriber
 
     private function getMethodsToParse(): \Generator
     {
-        foreach ($this->routeCollection->all() as $route) {
+        foreach ($this->routeCollection->all() as $routeName => $route) {
             if (!$route->hasDefault('_controller')) {
                 continue;
             }
@@ -161,7 +165,7 @@ final class OpenApiPhpDescriber
 
                 continue;
             }
-            yield $reflectedMethod => [$path, $supportedHttpMethods];
+            yield $reflectedMethod => [$path, $supportedHttpMethods, $routeName];
         }
     }
 
diff --git a/Tests/Functional/Controller/ApiController.php b/Tests/Functional/Controller/ApiController.php
index 4a40897..69372d3 100644
--- a/Tests/Functional/Controller/ApiController.php
+++ b/Tests/Functional/Controller/ApiController.php
@@ -26,7 +26,7 @@ use OpenApi\Annotations as OA;
 use Symfony\Component\Routing\Annotation\Route;
 
 /**
- * @Route("/api", host="api.example.com")
+ * @Route("/api", name="api_", host="api.example.com")
  */
 class ApiController
 {
@@ -232,4 +232,23 @@ class ApiController
     public function discriminatorMappingAction()
     {
     }
+
+    /**
+     * @Route("/named_route-operation-id", name="named_route_operation_id", methods={"GET", "POST"})
+     *
+     * @OA\Response(response=200, description="success")
+     */
+    public function namedRouteOperationIdAction()
+    {
+    }
+
+    /**
+     * @Route("/custom-operation-id", methods={"GET", "POST"})
+     *
+     * @Operation(operationId="custom-operation-id")
+     * @OA\Response(response=200, description="success")
+     */
+    public function customOperationIdAction()
+    {
+    }
 }
diff --git a/Tests/Functional/FunctionalTest.php b/Tests/Functional/FunctionalTest.php
index 8b2b372..6094466 100644
--- a/Tests/Functional/FunctionalTest.php
+++ b/Tests/Functional/FunctionalTest.php
@@ -506,7 +506,25 @@ class FunctionalTest extends WebTestCase
     public function testDefaultOperationId()
     {
         $operation = $this->getOperation('/api/article/{id}', 'get');
-        $this->assertNull($operation->operationId);
+        $this->assertEquals('get_api_nelmio_apidoc_tests_functional_api_fetcharticle', $operation->operationId);
+    }
+
+    public function testNamedRouteOperationId()
+    {
+        $operation = $this->getOperation('/api/named_route-operation-id', 'get');
+        $this->assertEquals('get_api_named_route_operation_id', $operation->operationId);
+
+        $operation = $this->getOperation('/api/named_route-operation-id', 'post');
+        $this->assertEquals('post_api_named_route_operation_id', $operation->operationId);
+    }
+
+    public function testCustomOperationId()
+    {
+        $operation = $this->getOperation('/api/custom-operation-id', 'get');
+        $this->assertEquals('custom-operation-id', $operation->operationId);
+
+        $operation = $this->getOperation('/api/custom-operation-id', 'post');
+        $this->assertEquals('custom-operation-id', $operation->operationId);
     }
 
     /**