diff --git a/src/main/java/dan200/computercraft/shared/peripheral/speaker/SpeakerPeripheral.java b/src/main/java/dan200/computercraft/shared/peripheral/speaker/SpeakerPeripheral.java
index 79c19bf60..995a326e9 100644
--- a/src/main/java/dan200/computercraft/shared/peripheral/speaker/SpeakerPeripheral.java
+++ b/src/main/java/dan200/computercraft/shared/peripheral/speaker/SpeakerPeripheral.java
@@ -202,7 +202,7 @@ public class SpeakerPeripheral implements IPeripheral {
 
         if (arguments.length > 2)
         {
-            if (!(arguments[1] instanceof Double))  // Arg wrong type
+            if (!(arguments[2] instanceof Double))  // Arg wrong type
             {
                 throw new LuaException("Expected string, number (optional), number (optional)");
             }