diff --git a/src/Infer/Analyzer/ClassAnalyzer.php b/src/Infer/Analyzer/ClassAnalyzer.php
index d5b1ebe9..7fe94f23 100644
--- a/src/Infer/Analyzer/ClassAnalyzer.php
+++ b/src/Infer/Analyzer/ClassAnalyzer.php
@@ -29,7 +29,7 @@ private function shouldAnalyzeParentClass(ReflectionClass $parentClassReflection
          * Classes from `vendor` aren't analyzed at the moment. Instead, it is up to developers to provide
          * definitions for them using the dictionaries.
          */
-        return ! str_contains($parentClassReflection->getFileName(), '/vendor/');
+        return ! str_contains($parentClassReflection->getFileName(), DIRECTORY_SEPARATOR.'vendor'.DIRECTORY_SEPARATOR);
     }
 
     /**
diff --git a/src/Infer/Services/ReferenceTypeResolver.php b/src/Infer/Services/ReferenceTypeResolver.php
index 99150c02..b050154a 100644
--- a/src/Infer/Services/ReferenceTypeResolver.php
+++ b/src/Infer/Services/ReferenceTypeResolver.php
@@ -346,7 +346,7 @@ private function resolveUnknownClassResolver(string $className): ?ClassDefinitio
         try {
             $reflection = new \ReflectionClass($className);
 
-            if (Str::contains($reflection->getFileName(), '/vendor/')) {
+            if (Str::contains($reflection->getFileName(), DIRECTORY_SEPARATOR.'vendor'.DIRECTORY_SEPARATOR)) {
                 Context::getInstance()->extensionsBroker->afterClassDefinitionCreated(new ClassDefinitionCreatedEvent($className, new ClassDefinition($className)));
 
                 return $this->index->getClassDefinition($className);