diff --git a/src/lfs.c b/src/lfs.c
index 020267d..8b4cfd2 100644
--- a/src/lfs.c
+++ b/src/lfs.c
@@ -197,15 +197,23 @@ static int get_dir (lua_State *L) {
 ** Check if the given element on the stack is a file and returns it.
 */
 static FILE *check_file (lua_State *L, int idx, const char *funcname) {
+#if LUA_VERSION_NUM == 501
         FILE **fh = (FILE **)luaL_checkudata (L, idx, "FILE*");
-        if (fh == NULL) {
-                luaL_error (L, "%s: not a file", funcname);
-                return 0;
-        } else if (*fh == NULL) {
+        if (*fh == NULL) {
                 luaL_error (L, "%s: closed file", funcname);
                 return 0;
         } else
                 return *fh;
+#elif LUA_VERSION_NUM >= 502 && LUA_VERSION_NUM <= 503
+        luaL_Stream *fh = (luaL_Stream *)luaL_checkudata (L, idx, "FILE*");
+        if (fh->closef == 0 || fh->f == NULL) {
+                luaL_error (L, "%s: closed file", funcname);
+                return 0;
+        } else
+                return fh->f;
+#else
+#error unsupported Lua version
+#endif
 }