diff --git a/demo/src/main/java/overrun/marshal/test/CMarshalTest.java b/demo/src/main/java/overrun/marshal/test/CMarshalTest.java
index 72abc02..7c5741d 100644
--- a/demo/src/main/java/overrun/marshal/test/CMarshalTest.java
+++ b/demo/src/main/java/overrun/marshal/test/CMarshalTest.java
@@ -51,6 +51,8 @@ public interface CMarshalTest {
 
     MemorySegment testWithArgAndReturnValue(MemorySegment segment);
 
+    @Custom("""
+        return testWithArgAndReturnValue(MemorySegment.NULL);""")
     MemorySegment testWithCustomBody();
 
     @Native(scope = MarshalScope.PRIVATE)
@@ -64,7 +66,7 @@ public interface CMarshalTest {
     void testWithRefArray(MemorySegment arr0, MemorySegment arr1, MemorySegment arr2, MemorySegment arr3, MemorySegment arr4, MemorySegment arr5);
 
     @Overload
-    void testWithRefArray(int[] arr0, @Ref int[] arr1, @Ref(nullable = true) int[] arr2, boolean[] arr3, @Ref boolean[] arr4, int[] arr5);
+    void testWithRefArray(int[] arr0, @Ref int[] arr1, @Ref(nullable = true) int[] arr2, boolean[] arr3, @Ref boolean[] arr4, @FixedSize(3) int[] arr5);
 
     void testWithString(MemorySegment str);
 
diff --git a/src/main/java/overrun/marshal/Custom.java b/src/main/java/overrun/marshal/Custom.java
new file mode 100644
index 0000000..45966c3
--- /dev/null
+++ b/src/main/java/overrun/marshal/Custom.java
@@ -0,0 +1,30 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2023 Overrun Organization
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ */
+
+package overrun.marshal;
+
+import java.lang.annotation.*;
+
+/**
+ * @author squid233
+ * @since 0.1.0
+ */
+@Documented
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.SOURCE)
+public @interface Custom {
+    String value();
+}
diff --git a/src/main/java/overrun/marshal/FixedSize.java b/src/main/java/overrun/marshal/FixedSize.java
new file mode 100644
index 0000000..2b6ff9c
--- /dev/null
+++ b/src/main/java/overrun/marshal/FixedSize.java
@@ -0,0 +1,30 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2023 Overrun Organization
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ */
+
+package overrun.marshal;
+
+import java.lang.annotation.*;
+
+/**
+ * @author squid233
+ * @since 0.1.0
+ */
+@Documented
+@Target(ElementType.PARAMETER)
+@Retention(RetentionPolicy.SOURCE)
+public @interface FixedSize {
+    int value();
+}