diff --git a/Specs/SpecGenerator.php b/Specs/SpecGenerator.php
index e7dc959..ca9e1d9 100644
--- a/Specs/SpecGenerator.php
+++ b/Specs/SpecGenerator.php
@@ -94,6 +94,7 @@ public function generateSpec(array $pluginNames, string $format = 'json', string
             }
 
             $pluginAnnotationsSource = $this->specPathResolver->getAnnotationFilePath($pluginName);
+            $this->loadAnnotationSourceIfNeeded($pluginAnnotationsSource);
             try {
                 $openapi = (new Generator(StaticContainer::get(NullLogger::class)))->generate([
                     $pluginAnnotationsSource,
@@ -108,6 +109,9 @@ public function generateSpec(array $pluginNames, string $format = 'json', string
         }
 
         $generator = new Generator(StaticContainer::get(LoggerInterface::class));
+        foreach ($pluginDirs as $pluginDir) {
+            $this->loadAnnotationSourceIfNeeded($pluginDir);
+        }
         $openapi = $generator->setVersion(OpenApi::VERSION_3_1_0)->generate(array_merge([
             $currentPluginDir . '/Annotations/GlobalApiComponents.php',
         ], $pluginDirs));
@@ -137,4 +141,13 @@ public function generateSpec(array $pluginNames, string $format = 'json', string
 
         return $specContents;
     }
+
+    private function loadAnnotationSourceIfNeeded(string $annotationSource): void
+    {
+        if (!is_file($annotationSource) || pathinfo($annotationSource, PATHINFO_EXTENSION) !== 'php') {
+            return;
+        }
+
+        require_once $annotationSource;
+    }
 }