diff --git a/src/CompilerBase.php b/src/CompilerBase.php
index fab95bf8..310a79b7 100644
--- a/src/CompilerBase.php
+++ b/src/CompilerBase.php
@@ -1017,10 +1017,13 @@ class CompilerBase implements PropertyAccessContext
 
     protected function getFullClassName(): string
     {
-        // 在接口上下文中，$this->class 为空但 $this->interface 已设置，
-        // `self` 类型声明应解析为接口自身的完整名称。
-        $classLike = $this->class !== '' ? $this->class : $this->interface;
-        return ltrim($this->namespace . '\\' . $classLike, '\\');
+        return ltrim($this->namespace . '\\' . $this->class, '\\');
+    }
+
+    protected function getFullClassLikeName(): string
+    {
+        $name = $this->class !== '' ? $this->class : $this->interface;
+        return ltrim($this->namespace . '\\' . $name, '\\');
     }
 
     protected function getFullMethodName(string $fullClassName, string $method): string
diff --git a/src/Generator/TypeCheckGenerator.php b/src/Generator/TypeCheckGenerator.php
index 16dc4ae3..292967a1 100644
--- a/src/Generator/TypeCheckGenerator.php
+++ b/src/Generator/TypeCheckGenerator.php
@@ -104,7 +104,7 @@ trait TypeCheckGenerator
         }
 
         if ($name === 'self') {
-            $class = $this->getFullClassName();
+            $class = $this->getFullClassLikeName();
         } elseif ($name === 'parent') {
             $class = $this->classDef->extends ?? '';
         } elseif ($name === 'static') {
diff --git a/src/Resolver/NameResolutionTrait.php b/src/Resolver/NameResolutionTrait.php
index 307117e5..827db4a3 100644
--- a/src/Resolver/NameResolutionTrait.php
+++ b/src/Resolver/NameResolutionTrait.php
@@ -166,7 +166,7 @@ trait NameResolutionTrait
                 return $this->getTypeFromZendType($typeNameLower);
             } else {
                 if ($typeName === 'self') {
-                    $class = $this->getFullClassName();
+                    $class = $this->getFullClassLikeName();
                 } elseif ($typeName === 'parent') {
                     if (!$this->classDef) {
                         $this->fatalError($type, 'Cannot use "parent" type declaration outside a class');
diff --git a/tests/compiler/namespace/interface-self-return-namespaced.phpt b/tests/compiler/namespace/interface-self-return-namespaced.phpt
index cfda0bad..4d05a98a 100644
--- a/tests/compiler/namespace/interface-self-return-namespaced.phpt
+++ b/tests/compiler/namespace/interface-self-return-namespaced.phpt
@@ -7,6 +7,10 @@ namespace App {
     interface Chainable
     {
         public function chain(): self;
+
+        public function maybe(bool $present): ?self;
+
+        public function combine(self $other): self;
     }
 
     // comment inside a named namespace block (Stmt_Nop)
@@ -19,6 +23,16 @@ namespace App {
             $this->log[] = 'chain';
             return $this;
         }
+
+        public function maybe(bool $present): ?self
+        {
+            return $present ? $this : null;
+        }
+
+        public function combine(Chainable $other): self
+        {
+            return $this;
+        }
     }
 }
 
@@ -28,9 +42,15 @@ namespace {
         $w = new \App\Widget();
         var_dump($w->chain()->chain() instanceof \App\Chainable);
         var_dump(count($w->log));
+        var_dump($w->maybe(true) instanceof \App\Chainable);
+        var_dump($w->maybe(false));
+        var_dump($w->combine(new \App\Widget()) === $w);
     }
 }
 ?>
 --EXPECT--
 bool(true)
 int(2)
+bool(true)
+NULL
+bool(true)