diff --git a/anselme/stdlib/number.lua b/anselme/stdlib/number.lua
index a3975e5..0e24300 100644
--- a/anselme/stdlib/number.lua
+++ b/anselme/stdlib/number.lua
@@ -44,7 +44,16 @@ return {
 	{ "_-_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number - b.number) end },
 	{ "_*_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number * b.number) end },
 	{ "_/_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number / b.number) end },
-	{ "_//_", "(a::is number, b::is number)", function(state, a, b) return Number:new(math.floor(a.number / b.number)) end },
+	{
+		"_//_", "(a::is number, b::is number)", function(state, a, b)
+			local r = a.number / b.number
+			if r < 0 then
+				return Number:new(math.ceil(r))
+			else
+				return Number:new(math.floor(r))
+			end
+		end
+	},
 	{ "_%_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number % b.number) end },
 	{ "_^_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number ^ b.number) end },
 	{ "-_", "(a::is number)", function(state, a) return Number:new(-a.number) end },