diff --git a/src/ffi/lua51/lua.rs b/src/ffi/lua51/lua.rs
index 3ad2db5..6c99503 100644
--- a/src/ffi/lua51/lua.rs
+++ b/src/ffi/lua51/lua.rs
@@ -67,7 +67,10 @@ pub const LUA_MINSTACK: c_int = 20;
 pub type lua_Number = c_double;
 
 /// A Lua integer, usually equivalent to `i64`
-pub type lua_Integer = isize;
+#[cfg(target_pointer_width = "32")]
+pub type lua_Integer = i32;
+#[cfg(target_pointer_width = "64")]
+pub type lua_Integer = i64;
 
 /// Type for native C functions that can be passed to Lua.
 pub type lua_CFunction = unsafe extern "C" fn(L: *mut lua_State) -> c_int;
diff --git a/src/ffi/lua52/lua.rs b/src/ffi/lua52/lua.rs
index 44097da..f8c7108 100644
--- a/src/ffi/lua52/lua.rs
+++ b/src/ffi/lua52/lua.rs
@@ -69,7 +69,10 @@ pub const LUA_RIDX_LAST: lua_Integer = LUA_RIDX_GLOBALS;
 pub type lua_Number = c_double;
 
 /// A Lua integer, usually equivalent to `i64`
-pub type lua_Integer = isize;
+#[cfg(target_pointer_width = "32")]
+pub type lua_Integer = i32;
+#[cfg(target_pointer_width = "64")]
+pub type lua_Integer = i64;
 
 /// A Lua unsigned integer, equivalent to `u32` in Lua 5.2
 pub type lua_Unsigned = c_uint;