diff --git a/sha2.lua b/sha2.lua
index 201f52e..3960502 100644
--- a/sha2.lua
+++ b/sha2.lua
@@ -117,7 +117,7 @@ assert(Lua_has_int64 or Lua_has_int32 or not Lua_has_integers, "Lua integers mus
 --   Using "int128" instead of "int64" is not OK: "int128" would require different branch of implementation for optimized SHA512.
 
 -- Check for LuaJIT and 32-bit bitwise libraries
-local is_LuaJIT = ({false, [1] = true})[1] and _VERSION ~= "Luau" and (type(jit) ~= "table" or jit.version_num >= 20000)  -- LuaJIT 1.x.x and Luau are treated as vanilla Lua 5.1/5.2
+local is_LuaJIT = ({false, [1] = true})[1] and string.sub(_VERSION, 1, 4) ~= "Luau" and (type(jit) ~= "table" or jit.version_num >= 20000)  -- LuaJIT 1.x.x and Luau are treated as vanilla Lua 5.1/5.2
 local is_LuaJIT_21  -- LuaJIT 2.1+
 local LuaJIT_arch
 local ffi           -- LuaJIT FFI library (as a table)