diff --git a/3rd/lua/lstring.c b/3rd/lua/lstring.c
index 29372c6a..d21b44f4 100644
--- a/3rd/lua/lstring.c
+++ b/3rd/lua/lstring.c
@@ -60,7 +60,7 @@ void luaS_share (TString *ts) {
   if (ts == NULL || isshared(ts))
     return;
   makeshared(ts);
-  ts->id = ATOM_DEC(&STRID);
+  ts->id = ATOM_FDEC(&STRID)-1;
 }
 
 unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {