diff --git a/code/modules/unit_tests/biome_lists.dm b/code/modules/unit_tests/biome_lists.dm
index 24d931bbd7fa..8f29a4109a37 100644
--- a/code/modules/unit_tests/biome_lists.dm
+++ b/code/modules/unit_tests/biome_lists.dm
@@ -2,12 +2,14 @@
 	for(var/biome_type as anything in SSmapping.biomes)
 		var/datum/biome/biome = SSmapping.biomes[biome_type]
 
-		validate_chance(biome.mob_spawn_chance, "mob spawn")
-		validate_chance(biome.flora_spawn_chance, "flora spawn")
-		validate_chance(biome.feature_spawn_chance, "feature spawn")
+		validate_chance(biome.mob_spawn_list, "mob spawn", biome_type)
+		validate_chance(biome.flora_spawn_list, "flora spawn", biome_type)
+		validate_chance(biome.feature_spawn_list, "feature spawn", biome_type)
 
-/datum/unit_test/biome_lists/proc/validate_chance(list/to_check, name)
+/datum/unit_test/biome_lists/proc/validate_chance(list/to_check, name, biome)
+	if(!islist(to_check))
+		TEST_FAIL("Biome [biome] has invalid [name] list")
 	for(var/type in to_check)
 		var/value = to_check[type]
 		if(!isnum(value) || value < 1 || value != round(value))
-			TEST_FAIL("Biome [name] has invalid [name] chance for [type] ([value])")
+			TEST_FAIL("Biome [biome] has invalid [name] chance for [type] ([value])")