diff --git a/src/progressive.lua b/src/progressive.lua
index e3a5141..184bf20 100644
--- a/src/progressive.lua
+++ b/src/progressive.lua
@@ -89,6 +89,10 @@ local item_lists = {"main", "craft", "craftpreview"}
 
 local function get_inv_items(player)
 	local inv = player:get_inventory()
+	if not inv then
+		return {}
+	end
+
 	local stacks = {}
 
 	for i = 1, #item_lists do