diff --git a/constants/npc_trade_constants.asm b/constants/npc_trade_constants.asm
index 044b2e4fa..f505bf959 100644
--- a/constants/npc_trade_constants.asm
+++ b/constants/npc_trade_constants.asm
@@ -38,6 +38,7 @@ DEF NUM_NPC_TRADES EQU const_value
 	const TRADE_DIALOG_WRONG
 	const TRADE_DIALOG_COMPLETE
 	const TRADE_DIALOG_AFTER
+DEF NUM_TRADE_DIALOGS EQU const_value
 
 ; trade dialog sets
 	const_def
@@ -45,3 +46,4 @@ DEF NUM_NPC_TRADES EQU const_value
 	const TRADE_DIALOGSET_HAPPY
 	const TRADE_DIALOGSET_NEWBIE
 	const TRADE_DIALOGSET_GIRL
+DEF NUM_TRADE_DIALOGSETS EQU const_value
diff --git a/engine/events/npc_trade.asm b/engine/events/npc_trade.asm
index b0c0c9dd5..898a2e61c 100644
--- a/engine/events/npc_trade.asm
+++ b/engine/events/npc_trade.asm
@@ -405,6 +405,7 @@ PrintTradeText:
 
 TradeTexts:
 ; entries correspond to TRADE_DIALOG_* × TRADE_DIALOGSET_* constants
+	table_width 2
 ; TRADE_DIALOG_INTRO
 	dw NPCTradeIntroText1
 	dw NPCTradeIntroText2
@@ -430,6 +431,7 @@ TradeTexts:
 	dw NPCTradeAfterText2
 	dw NPCTradeAfterText4
 	dw NPCTradeAfterText3
+	assert_table_length NUM_TRADE_DIALOGS * NUM_TRADE_DIALOGSETS
 
 NPCTradeCableText:
 	text_far _NPCTradeCableText