diff --git a/src/main/java/com/r35157/driver/ledsign/LedSign.java b/src/main/java/com/r35157/driver/ledsign/LedSign.java
index 5787d89..a8d1a1f 100644
--- a/src/main/java/com/r35157/driver/ledsign/LedSign.java
+++ b/src/main/java/com/r35157/driver/ledsign/LedSign.java
@@ -1,5 +1,7 @@
 package com.r35157.driver.ledsign;
 
+import org.jetbrains.annotations.NotNull;
+
 public interface LedSign {
-    void sendCommand(byte[] payload);
+    void sendCommand(@NotNull byte[] payload);
 }