diff --git a/src/lib_jit.c b/src/lib_jit.c
index ef6fd465..52368a8b 100644
--- a/src/lib_jit.c
+++ b/src/lib_jit.c
@@ -188,7 +188,7 @@ LJLIB_CF(jit_util_funcinfo)
       setintfield(L, t, "currentline", pt->lineinfo ? pt->lineinfo[pc-1] : 0);
     lua_pushboolean(L, (pt->flags & PROTO_IS_VARARG));
     lua_setfield(L, -2, "isvararg");
-    setstrV(L, L->top++, pt->chunkname);
+    setstrV(L, L->top++, proto_chunkname(pt));
     lua_setfield(L, -2, "source");
     lj_err_pushloc(L, pt, pc);
     lua_setfield(L, -2, "loc");
@@ -246,7 +246,7 @@ LJLIB_CF(jit_util_funcuvname)
   GCproto *pt = check_Lproto(L, 0);
   uint32_t idx = (uint32_t)lj_lib_checkint(L, 2);
   if (idx < pt->sizeuvname) {
-    setstrV(L, L->top-1, pt->uvname[idx]);
+    setstrV(L, L->top-1, gco2str(proto_uvname(pt, idx)));
     return 1;
   }
   return 0;
diff --git a/src/lj_api.c b/src/lj_api.c
index a2d29723..8216c395 100644
--- a/src/lj_api.c
+++ b/src/lj_api.c
@@ -813,7 +813,7 @@ static const char *aux_upvalue(cTValue *f, uint32_t idx, TValue **val)
     GCproto *pt = funcproto(fn);
     if (idx < pt->sizeuvname) {
       *val = uvval(&gcref(fn->l.uvptr[idx])->uv);
-      return strdata(pt->uvname[idx]);
+      return strdata(gco2str(proto_uvname(pt, idx)));
     }
   } else {
     if (idx < fn->c.nupvalues) {
diff --git a/src/lj_err.c b/src/lj_err.c
index d1e705ea..0c54cf62 100644
--- a/src/lj_err.c
+++ b/src/lj_err.c
@@ -176,7 +176,8 @@ restart:
 	}
 	return "field";
       case BC_UGET:
-	*name = pt->uvname ? strdata(pt->uvname[bc_d(ins)]) : "?";
+	*name = mref(pt->uvname, GCRef) ?
+		strdata(gco2str(proto_uvname(pt,bc_d(ins)))) : "?";
 	return "upvalue";
       default:
 	return NULL;
@@ -217,7 +218,7 @@ static const char *getfuncname(lua_State *L, TValue *frame, const char **name)
 
 void lj_err_pushloc(lua_State *L, GCproto *pt, BCPos pc)
 {
-  GCstr *name = pt->chunkname;
+  GCstr *name = proto_chunkname(pt);
   if (name) {
     const char *s = strdata(name);
     MSize i, len = name->len;
@@ -344,7 +345,7 @@ LUA_API int lua_getinfo(lua_State *L, const char *what, lua_Debug *ar)
     switch (*what) {
     case 'S':
       if (isluafunc(fn)) {
-	ar->source = strdata(funcproto(fn)->chunkname);
+	ar->source = strdata(proto_chunkname(funcproto(fn)));
 	ar->linedefined = cast_int(funcproto(fn)->linedefined);
 	ar->lastlinedefined = cast_int(funcproto(fn)->lastlinedefined);
 	ar->what = (ar->linedefined == 0) ? "main" : "Lua";
@@ -819,7 +820,7 @@ LJ_NOINLINE static void err_loc(lua_State *L, const char *msg,
     if (isluafunc(fn)) {
       char buff[LUA_IDSIZE];
       BCLine line = currentline(L, fn, nextframe);
-      err_chunkid(buff, strdata(funcproto(fn)->chunkname));
+      err_chunkid(buff, strdata(proto_chunkname(funcproto(fn))));
       lj_str_pushf(L, "%s:%d: %s", buff, line, msg);
       return;
     }
diff --git a/src/lj_func.c b/src/lj_func.c
index 27a8322f..284bd3b3 100644
--- a/src/lj_func.c
+++ b/src/lj_func.c
@@ -28,7 +28,7 @@ GCproto *lj_func_newproto(lua_State *L)
   pt->trace = 0;
   setmref(pt->k, NULL);
   setmref(pt->bc, NULL);
-  pt->uv = NULL;
+  setmref(pt->uv, NULL);
   pt->sizebc = 0;
   pt->sizekgc = 0;
   pt->sizekn = 0;
@@ -39,8 +39,8 @@ GCproto *lj_func_newproto(lua_State *L)
   pt->lastlinedefined = 0;
   pt->lineinfo = NULL;
   pt->varinfo = NULL;
-  pt->uvname = NULL;
-  pt->chunkname = NULL;
+  setmref(pt->uvname, NULL);
+  setgcrefnull(pt->chunkname);
   return pt;
 }
 
@@ -51,10 +51,10 @@ void LJ_FASTCALL lj_func_freeproto(global_State *g, GCproto *pt)
 		pt->sizekn*(MSize)sizeof(lua_Number);
   lj_mem_free(g, mref(pt->k, GCRef) - nkgc, sizek);
   lj_mem_freevec(g, proto_bc(pt), pt->sizebc, BCIns);
-  lj_mem_freevec(g, pt->uv, pt->sizeuv, uint16_t);
+  lj_mem_freevec(g, proto_uv(pt), pt->sizeuv, uint16_t);
   lj_mem_freevec(g, pt->lineinfo, pt->sizelineinfo, int32_t);
   lj_mem_freevec(g, pt->varinfo, pt->sizevarinfo, struct VarInfo);
-  lj_mem_freevec(g, pt->uvname, pt->sizeuvname, GCstr *);
+  lj_mem_freevec(g, mref(pt->uvname, GCRef), pt->sizeuvname, GCRef);
   lj_trace_freeproto(g, pt);
   lj_mem_freet(g, pt);
 }
@@ -169,7 +169,7 @@ GCfunc *lj_func_newL_gc(lua_State *L, GCproto *pt, GCfuncL *parent)
   nuv = fn->l.nupvalues;
   base = L->base;
   for (i = 0; i < nuv; i++) {
-    uint32_t v = pt->uv[i];
+    uint32_t v = proto_uv(pt)[i];
     GCupval *uv;
     if ((v & 0x8000)) {
       uv = func_finduv(L, base + (v & 0xff));
diff --git a/src/lj_gc.c b/src/lj_gc.c
index 9f0ff2b6..3c1b847a 100644
--- a/src/lj_gc.c
+++ b/src/lj_gc.c
@@ -251,13 +251,13 @@ static void gc_traverse_proto(global_State *g, GCproto *pt)
   }
 #endif
   /* GC during prototype creation could cause NULL fields. */
-  if (pt->chunkname)
-    gc_mark_str(pt->chunkname);
+  if (gcref(pt->chunkname))
+    gc_mark_str(proto_chunkname(pt));
   for (i = -(ptrdiff_t)pt->sizekgc; i < 0; i++)  /* Mark collectable consts. */
     gc_markobj(g, proto_kgc(pt, i));
   for (i = 0; i < (ptrdiff_t)pt->sizeuvname; i++)  /* Mark upvalue names. */
-    if (pt->uvname[i])
-      gc_mark_str(pt->uvname[i]);
+    if (proto_uvname(pt, i))
+      gc_mark_str(gco2str(proto_uvname(pt, i)));
   for (i = 0; i < (ptrdiff_t)pt->sizevarinfo; i++)  /* Mark names of locals. */
     if (pt->varinfo[i].name)
       gc_mark_str(pt->varinfo[i].name);
@@ -332,7 +332,7 @@ static size_t propagatemark(global_State *g)
 			     sizeof(uint16_t) * pt->sizeuv +
 			     sizeof(int32_t) * pt->sizelineinfo +
 			     sizeof(VarInfo) * pt->sizevarinfo +
-			     sizeof(GCstr *) * pt->sizeuvname;
+			     sizeof(GCRef) * pt->sizeuvname;
   } else {
     lua_State *th = gco2th(o);
     setgcrefr(th->gclist, g->gc.grayagain);
diff --git a/src/lj_gdbjit.c b/src/lj_gdbjit.c
index 6fb8a1d3..af31b277 100644
--- a/src/lj_gdbjit.c
+++ b/src/lj_gdbjit.c
@@ -709,7 +709,7 @@ void lj_gdbjit_addtrace(jit_State *J, Trace *T, TraceNo traceno)
     ctx.lineno = pt->lineinfo ? pt->lineinfo[proto_bcpos(pt, startpc)] : 0;
   else
     ctx.lineno = pt->linedefined;
-  ctx.filename = strdata(pt->chunkname);
+  ctx.filename = strdata(proto_chunkname(pt));
   if (*ctx.filename == '@' || *ctx.filename == '=')
     ctx.filename++;
   else
diff --git a/src/lj_obj.h b/src/lj_obj.h
index 22b69c60..164ec853 100644
--- a/src/lj_obj.h
+++ b/src/lj_obj.h
@@ -352,7 +352,7 @@ typedef struct GCproto {
   GCRef gclist;
   MRef k;		/* Split constant array (points to the middle). */
   MRef bc;		/* Array of bytecode instructions. */
-  uint16_t *uv;		/* Upvalue list. local slot|0x8000 or parent uv idx. */
+  MRef uv;		/* Upvalue list. local slot|0x8000 or parent uv idx. */
   MSize sizekgc;	/* Number of collectable constants. */
   MSize sizekn;		/* Number of lua_Number constants. */
   uint8_t sizeuv;	/* Number of upvalues. */
@@ -366,8 +366,8 @@ typedef struct GCproto {
   BCLine lastlinedefined;  /* Last line of the function definition. */
   BCLine *lineinfo;	/* Map from bytecode instructions to source lines. */
   struct VarInfo *varinfo;  /* Names and extents of local variables. */
-  GCstr **uvname;	/* Upvalue names. */
-  GCstr *chunkname;	/* Name of the chunk this function was defined in. */
+  MRef uvname;		/* Array of upvalue names (GCRef of GCstr). */
+  GCRef chunkname;	/* Name of the chunk this function was defined in. */
 } GCproto;
 
 #define PROTO_IS_VARARG		0x01
@@ -388,6 +388,11 @@ typedef struct GCproto {
 #define proto_insptr(pt, pos) \
   check_exp((uintptr_t)(pos) < (pt)->sizebc, &proto_bc(pt)[(pos)])
 #define proto_bcpos(pt, pc)	((BCPos)((pc) - proto_bc(pt)))
+#define proto_uv(pt)		(mref((pt)->uv, uint16_t))
+#define proto_uvname(pt, idx) \
+  check_exp((uintptr_t)(idx) < (pt)->sizeuvname, \
+	    gcref(mref((pt)->uvname, GCRef)[(idx)]))
+#define proto_chunkname(pt)	(gco2str(gcref((pt)->chunkname)))
 
 /* -- Upvalue object ------------------------------------------------------ */
 
diff --git a/src/lj_parse.c b/src/lj_parse.c
index 1a596d72..864f9e20 100644
--- a/src/lj_parse.c
+++ b/src/lj_parse.c
@@ -1017,20 +1017,23 @@ static uint32_t indexupvalue(FuncState *fs, GCstr *name, ExpDesc *v)
 {
   uint32_t i;
   GCproto *pt = fs->pt;
+  GCRef *uvname;
   for (i = 0; i < fs->nuv; i++) {
     if (fs->upvalues[i].info == v->u.s.info && fs->upvalues[i].k == v->k) {
-      lua_assert(pt->uvname[i] == name);
+      lua_assert(gco2str(proto_uvname(pt, i)) == name);
       return i;
     }
   }
   /* Not found, create a new upvalue for this name. */
+  uvname = mref(pt->uvname, GCRef);
   if (LJ_UNLIKELY(fs->nuv >= pt->sizeuvname)) {
     MSize oldsize = pt->sizeuvname;
     checklimit(fs, fs->nuv, LJ_MAX_UPVAL, "upvalues");
-    lj_mem_growvec(fs->L, pt->uvname, pt->sizeuvname, LJ_MAX_UPVAL, GCstr *);
-    while (oldsize < pt->sizeuvname) pt->uvname[oldsize++] = NULL;
+    lj_mem_growvec(fs->L, uvname, pt->sizeuvname, LJ_MAX_UPVAL, GCRef);
+    setmref(pt->uvname, uvname);
+    while (oldsize < pt->sizeuvname) setgcrefnull(uvname[oldsize++]);
   }
-  pt->uvname[fs->nuv] = name;
+  setgcref(uvname[fs->nuv], obj2gco(name));
   lj_gc_objbarrier(fs->L, pt, name);
   lua_assert(v->k == VLOCAL || v->k == VUPVAL);
   fs->upvalues[fs->nuv].k = cast_byte(v->k);
@@ -1123,7 +1126,7 @@ static void open_func(LexState *ls, FuncState *fs)
   fs->nactvar = 0;
   fs->nuv = 0;
   fs->bl = NULL;
-  pt->chunkname = ls->chunkname;
+  setgcref(pt->chunkname, obj2gco(ls->chunkname));
   pt->framesize = 2;  /* registers 0/1 are always valid */
   fs->kt = lj_tab_new(L, 0, 0);
   /* anchor table of constants and prototype (to avoid being collected) */
@@ -1176,12 +1179,13 @@ static void collectk(FuncState *fs, GCproto *pt)
 static void collectuv(FuncState *fs, GCproto *pt)
 {
   uint32_t i;
-  pt->uv = lj_mem_newvec(fs->L, fs->nuv, uint16_t);
+  uint16_t *uv = lj_mem_newvec(fs->L, fs->nuv, uint16_t);
+  setmref(pt->uv, uv);
   pt->sizeuv = fs->nuv;
   for (i = 0; i < pt->sizeuv; i++) {
     uint32_t v = fs->upvalues[i].info;
     if (fs->upvalues[i].k == VLOCAL) v |= 0x8000;
-    pt->uv[i] = (uint16_t)v;
+    uv[i] = (uint16_t)v;
   }
 }
 
@@ -1228,6 +1232,7 @@ static void close_func(LexState *ls)
   FuncState *fs = ls->fs;
   GCproto *pt = fs->pt;
   BCIns *bc;
+  GCRef *uvname;
   removevars(ls, 0);
   finalret(fs, pt);
   bc = proto_bc(pt);
@@ -1240,7 +1245,9 @@ static void close_func(LexState *ls)
   pt->sizelineinfo = fs->pc;
   lj_mem_reallocvec(L, pt->varinfo, pt->sizevarinfo, fs->nlocvars, VarInfo);
   pt->sizevarinfo = fs->nlocvars;
-  lj_mem_reallocvec(L, pt->uvname, pt->sizeuvname, fs->nuv, GCstr *);
+  uvname = mref(pt->uvname, GCRef);
+  lj_mem_reallocvec(L, uvname, pt->sizeuvname, fs->nuv, GCRef);
+  setmref(pt->uvname, uvname);
   pt->sizeuvname = fs->nuv;
   lua_assert(fs->bl == NULL);
   lj_vmevent_send(L, BC,