diff --git a/plugin/http/init.lua b/plugin/http/init.lua
index c72c2066..3d05c6d3 100644
--- a/plugin/http/init.lua
+++ b/plugin/http/init.lua
@@ -18,7 +18,7 @@ Http.Response = HttpResponse
 -- to a native Luau number. We should change the upstream decoder to emit a native
 -- integer, once those are live.
 function msgpack.UInt64.new(mostSignificantPart: number, leastSignificantPart: number): number
-	return mostSignificantPart * 2 ^ 32 + (leastSignificantPart % 2 ^ 32)
+	return (mostSignificantPart % 2 ^ 32) * 2 ^ 32 + (leastSignificantPart % 2 ^ 32)
 end
 
 local function performRequest(requestParams)