diff --git a/mappings/net/minecraft/network/packet/c2s/play/BookUpdateC2SPacket.mapping b/mappings/net/minecraft/network/packet/c2s/play/BookUpdateC2SPacket.mapping
index 0d69452907..3b4c81280d 100644
--- a/mappings/net/minecraft/network/packet/c2s/play/BookUpdateC2SPacket.mapping
+++ b/mappings/net/minecraft/network/packet/c2s/play/BookUpdateC2SPacket.mapping
@@ -1,8 +1,11 @@
 CLASS net/minecraft/class_2820 net/minecraft/network/packet/c2s/play/BookUpdateC2SPacket
 	FIELD field_12863 book Lnet/minecraft/class_1799;
 	FIELD field_12864 signed Z
+	FIELD field_26897 slot I
 	METHOD <init> (Lnet/minecraft/class_1799;ZI)V
 		ARG 1 book
 		ARG 2 signed
+		ARG 3 slot
+	METHOD method_12235 getSlot ()I
 	METHOD method_12237 getBook ()Lnet/minecraft/class_1799;
 	METHOD method_12238 wasSigned ()Z