diff --git a/constants/mart_constants.asm b/constants/mart_constants.asm
index 1a2d08fef..32b193cfa 100644
--- a/constants/mart_constants.asm
+++ b/constants/mart_constants.asm
@@ -5,6 +5,7 @@
 	const MARTTYPE_BARGAIN
 	const MARTTYPE_PHARMACY
 	const MARTTYPE_ROOFTOP
+DEF NUM_MART_TYPES EQU const_value
 
 ; Marts indexes (see data/items/marts.asm)
 	const_def
diff --git a/engine/items/mart.asm b/engine/items/mart.asm
index 8149fd709..e1c5010cb 100644
--- a/engine/items/mart.asm
+++ b/engine/items/mart.asm
@@ -12,16 +12,19 @@ OpenMartDialog::
 	ld [wMartType], a
 	call LoadMartPointer
 	ld a, [wMartType]
-	ld hl, .dialogs
+	ld hl, MartTypeDialogs
 	rst JumpTable
 	ret
 
-.dialogs
+MartTypeDialogs:
+; entries correspond to MARTTYPE_* constants
+	table_width 2
 	dw MartDialog
 	dw HerbShop
 	dw BargainShop
 	dw Pharmacist
 	dw RooftopSale
+	assert_table_length NUM_MART_TYPES
 
 MartDialog:
 	ld a, MARTTYPE_STANDARD