diff --git a/solitaire.lua b/solitaire.lua
index fa02df6..df1170e 100644
--- a/solitaire.lua
+++ b/solitaire.lua
@@ -335,7 +335,7 @@ function update()
 		local has_won=true
 		for i=3,6 do
 			local stack=stacks[i]
-			has_won=(has_won and stack[#stack].rank>=13)
+			has_won=(has_won and #stack>0 and stack[#stack].rank>=13)
 		end
 		if has_won then
 			pmem(WIN_COUNT_SLOT, pmem(WIN_COUNT_SLOT) + 1)