diff --git a/lfunc.c b/lfunc.c
index 9f91ad4..f7edf56 100644
--- a/lfunc.c
+++ b/lfunc.c
@@ -82,20 +82,22 @@
 
 
 /*
-** Find and reuse, or create if it does not exist, a regular upvalue
-** at the given level.
+** Find and reuse, or create if it does not exist, an upvalue
+** at the given level and set it to the given slot.
 */
-UpVal *luaF_findupval (lua_State *L, StkId level) {
+void luaF_setupval (lua_State *L, StkId level, UpVal **slot) {
   UpVal **pp = &L->openupval;
   UpVal *p;
   lua_assert(isintwups(L) || L->openupval == NULL);
   while ((p = *pp) != NULL && uplevel(p) >= level) {  /* search for it */
+    *slot = p;
     if (uplevel(p) == level && !isdead(G(L), p))  /* corresponding upvalue? */
-      return p;  /* return it */
+      return;  /* found it */
     pp = &p->u.open.next;
   }
-  /* not found: create a new upvalue after 'pp' */
-  return newupval(L, 0, level, pp);
+  /* not found: create a new upvalue after 'pp' (which is
+    anchored in 'slot', in case of an emergency collection) */
+  *slot = newupval(L, 0, level, pp);
 }
 
 
diff --git a/lfunc.h b/lfunc.h
index 0ed79c4..72fc913 100644
--- a/lfunc.h
+++ b/lfunc.h
@@ -57,7 +57,7 @@
 LUAI_FUNC CClosure *luaF_newCclosure (lua_State *L, int nelems);
 LUAI_FUNC LClosure *luaF_newLclosure (lua_State *L, int nelems);
 LUAI_FUNC void luaF_initupvals (lua_State *L, LClosure *cl);
-LUAI_FUNC UpVal *luaF_findupval (lua_State *L, StkId level);
+LUAI_FUNC void luaF_setupval (lua_State *L, StkId level, UpVal **slot);
 LUAI_FUNC void luaF_newtbcupval (lua_State *L, StkId level);
 LUAI_FUNC int luaF_close (lua_State *L, StkId level, int status);
 LUAI_FUNC void luaF_unlinkupval (UpVal *uv);
diff --git a/lvm.c b/lvm.c
index d9bd0ab..d3e0519 100644
--- a/lvm.c
+++ b/lvm.c
@@ -697,7 +697,7 @@
   setclLvalue2s(L, ra, ncl);  /* anchor new closure in stack */
   for (i = 0; i < nup; i++) {  /* fill in its upvalues */
     if (uv[i].instack)  /* upvalue refers to local variable? */
-      ncl->upvals[i] = luaF_findupval(L, base + uv[i].idx);
+      luaF_setupval(L, base + uv[i].idx, &ncl->upvals[i]);
     else  /* get upvalue from enclosing function */
       ncl->upvals[i] = encup[uv[i].idx];
     luaC_objbarrier(L, ncl, ncl->upvals[i]);