diff --git a/src/lib_jit.c b/src/lib_jit.c
index 52368a8b..d0b9e833 100644
--- a/src/lib_jit.c
+++ b/src/lib_jit.c
@@ -184,8 +184,9 @@ LJLIB_CF(jit_util_funcinfo)
     setintfield(L, t, "gcconsts", (int32_t)pt->sizekgc);
     setintfield(L, t, "nconsts", (int32_t)pt->sizekn);
     setintfield(L, t, "upvalues", (int32_t)pt->sizeuv);
-    if (pc > 0)
-      setintfield(L, t, "currentline", pt->lineinfo ? pt->lineinfo[pc-1] : 0);
+    if (pc-1 < pt->sizebc)
+      setintfield(L, t, "currentline",
+		  proto_lineinfo(pt) ? proto_line(pt, pc-1) : 0);
     lua_pushboolean(L, (pt->flags & PROTO_IS_VARARG));
     lua_setfield(L, -2, "isvararg");
     setstrV(L, L->top++, proto_chunkname(pt));
diff --git a/src/lj_dispatch.c b/src/lj_dispatch.c
index 09cb2f5d..5378531d 100644
--- a/src/lj_dispatch.c
+++ b/src/lj_dispatch.c
@@ -301,12 +301,12 @@ void LJ_FASTCALL lj_dispatch_ins(lua_State *L, const BCIns *pc)
     g->hookcount = g->hookcstart;
     callhook(L, LUA_HOOKCOUNT, -1);
   }
-  if ((g->hookmask & LUA_MASKLINE) && pt->lineinfo) {
+  if ((g->hookmask & LUA_MASKLINE) && proto_lineinfo(pt)) {
     BCPos npc = proto_bcpos(pt, pc) - 1;
     BCPos opc = proto_bcpos(pt, oldpc) - 1;
-    BCLine line = pt->lineinfo[npc];
+    BCLine line = proto_line(pt, npc);
     if (npc == 0 || pc <= oldpc ||
-	opc >= pt->sizebc || line != pt->lineinfo[opc]) {
+	opc >= pt->sizebc || line != proto_line(pt, opc)) {
       L->top = L->base + slots;  /* Fix top again after instruction hook. */
       callhook(L, LUA_HOOKLINE, line);
     }
diff --git a/src/lj_err.c b/src/lj_err.c
index 0c54cf62..cf7f9ae4 100644
--- a/src/lj_err.c
+++ b/src/lj_err.c
@@ -129,7 +129,7 @@ static BCLine currentline(lua_State *L, GCfunc *fn, cTValue *nextframe)
   if (pc != ~(BCPos)0) {
     GCproto *pt = funcproto(fn);
     lua_assert(pc < pt->sizebc);
-    return pt->lineinfo ? pt->lineinfo[pc] : 0;
+    return proto_lineinfo(pt) ? proto_line(pt, pc) : 0;
   } else {
     return -1;
   }
@@ -224,7 +224,7 @@ void lj_err_pushloc(lua_State *L, GCproto *pt, BCPos pc)
     MSize i, len = name->len;
     BCLine line;
     if (pc)
-      line = pt->lineinfo ? pt->lineinfo[pc-1] : 0;
+      line = proto_lineinfo(pt) ? proto_line(pt, pc-1) : 0;
     else
       line = pt->linedefined;
     if (*s == '@') {
@@ -377,10 +377,12 @@ LUA_API int lua_getinfo(lua_State *L, const char *what, lua_Debug *ar)
     case 'L':
       if (isluafunc(fn)) {
 	GCtab *t = lj_tab_new(L, 0, 0);
-	BCLine *lineinfo = funcproto(fn)->lineinfo;
-	uint32_t i, szl = funcproto(fn)->sizelineinfo;
-	for (i = 0; i < szl; i++)
-	  setboolV(lj_tab_setint(L, t, lineinfo[i]), 1);
+	BCLine *lineinfo = proto_lineinfo(funcproto(fn));
+	if (lineinfo) {
+	  uint32_t i, szl = funcproto(fn)->sizelineinfo;
+	  for (i = 0; i < szl; i++)
+	    setboolV(lj_tab_setint(L, t, lineinfo[i]), 1);
+	}
 	settabV(L, L->top, t);
       } else {
 	setnilV(L->top);
diff --git a/src/lj_func.c b/src/lj_func.c
index 284bd3b3..4354aa21 100644
--- a/src/lj_func.c
+++ b/src/lj_func.c
@@ -37,7 +37,7 @@ GCproto *lj_func_newproto(lua_State *L)
   pt->sizeuvname = 0;
   pt->linedefined = 0;
   pt->lastlinedefined = 0;
-  pt->lineinfo = NULL;
+  setmref(pt->lineinfo, NULL);
   pt->varinfo = NULL;
   setmref(pt->uvname, NULL);
   setgcrefnull(pt->chunkname);
@@ -52,7 +52,7 @@ void LJ_FASTCALL lj_func_freeproto(global_State *g, GCproto *pt)
   lj_mem_free(g, mref(pt->k, GCRef) - nkgc, sizek);
   lj_mem_freevec(g, proto_bc(pt), pt->sizebc, BCIns);
   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, proto_lineinfo(pt), pt->sizelineinfo, BCLine);
   lj_mem_freevec(g, pt->varinfo, pt->sizevarinfo, struct VarInfo);
   lj_mem_freevec(g, mref(pt->uvname, GCRef), pt->sizeuvname, GCRef);
   lj_trace_freeproto(g, pt);
diff --git a/src/lj_gc.c b/src/lj_gc.c
index 3c1b847a..04aa7161 100644
--- a/src/lj_gc.c
+++ b/src/lj_gc.c
@@ -330,7 +330,7 @@ static size_t propagatemark(global_State *g)
 			     sizeof(GCRef) * pt->sizekgc +
 			     sizeof(lua_Number) * pt->sizekn +
 			     sizeof(uint16_t) * pt->sizeuv +
-			     sizeof(int32_t) * pt->sizelineinfo +
+			     sizeof(BCLine) * pt->sizelineinfo +
 			     sizeof(VarInfo) * pt->sizevarinfo +
 			     sizeof(GCRef) * pt->sizeuvname;
   } else {
diff --git a/src/lj_gdbjit.c b/src/lj_gdbjit.c
index af31b277..e60a451b 100644
--- a/src/lj_gdbjit.c
+++ b/src/lj_gdbjit.c
@@ -706,7 +706,7 @@ void lj_gdbjit_addtrace(jit_State *J, Trace *T, TraceNo traceno)
   ctx.spadjp = CFRAME_SIZE + (MSize)(parent ? J->trace[parent]->spadjust : 0);
   ctx.spadj = CFRAME_SIZE + T->spadjust;
   if (startpc >= proto_bc(pt))
-    ctx.lineno = pt->lineinfo ? pt->lineinfo[proto_bcpos(pt, startpc)] : 0;
+    ctx.lineno = proto_lineinfo(pt) ? proto_line(pt,proto_bcpos(pt,startpc)): 0;
   else
     ctx.lineno = pt->linedefined;
   ctx.filename = strdata(proto_chunkname(pt));
diff --git a/src/lj_obj.h b/src/lj_obj.h
index 164ec853..cdb90dff 100644
--- a/src/lj_obj.h
+++ b/src/lj_obj.h
@@ -364,7 +364,7 @@ typedef struct GCproto {
   MSize sizeuvname;	/* Size of upvalue names array (may be 0). */
   BCLine linedefined;	/* First line of the function definition. */
   BCLine lastlinedefined;  /* Last line of the function definition. */
-  BCLine *lineinfo;	/* Map from bytecode instructions to source lines. */
+  MRef lineinfo;	/* Map from bytecode instructions to source lines. */
   struct VarInfo *varinfo;  /* Names and extents of local variables. */
   MRef uvname;		/* Array of upvalue names (GCRef of GCstr). */
   GCRef chunkname;	/* Name of the chunk this function was defined in. */
@@ -393,6 +393,9 @@ typedef struct GCproto {
   check_exp((uintptr_t)(idx) < (pt)->sizeuvname, \
 	    gcref(mref((pt)->uvname, GCRef)[(idx)]))
 #define proto_chunkname(pt)	(gco2str(gcref((pt)->chunkname)))
+#define proto_lineinfo(pt)	(mref((pt)->lineinfo, BCLine))
+#define proto_line(pt, pos) \
+  check_exp((uintptr_t)(pos) < (pt)->sizebc, proto_lineinfo(pt)[(pos)])
 
 /* -- Upvalue object ------------------------------------------------------ */
 
diff --git a/src/lj_parse.c b/src/lj_parse.c
index 864f9e20..a3291553 100644
--- a/src/lj_parse.c
+++ b/src/lj_parse.c
@@ -247,19 +247,22 @@ static void patchlist(FuncState *fs, BCPos list, BCPos target)
 static BCPos emitINS(FuncState *fs, BCIns i)
 {
   GCproto *pt;
+  BCIns *bc;
+  BCLine *lineinfo;
   patchlistaux(fs, fs->jpc, fs->pc, NO_REG, fs->pc);
   fs->jpc = NO_JMP;
   pt = fs->pt;
+  bc = proto_bc(pt);
+  lineinfo = proto_lineinfo(pt);
   if (LJ_UNLIKELY(fs->pc >= pt->sizebc)) {
-    BCIns *bc;
     checklimit(fs, fs->pc, LJ_MAX_BCINS, "bytecode instructions");
-    bc = proto_bc(pt);
     lj_mem_growvec(fs->L, bc, pt->sizebc, LJ_MAX_BCINS, BCIns);
     setmref(pt->bc, bc);
-    lj_mem_growvec(fs->L, pt->lineinfo, pt->sizelineinfo, LJ_MAX_BCINS, BCLine);
+    lj_mem_growvec(fs->L, lineinfo, pt->sizelineinfo, LJ_MAX_BCINS, BCLine);
+    setmref(pt->lineinfo, lineinfo);
   }
-  *proto_insptr(pt, fs->pc) = i;
-  pt->lineinfo[fs->pc] = fs->ls->lastline;
+  bc[fs->pc] = i;
+  lineinfo[fs->pc] = fs->ls->lastline;
   return fs->pc++;
 }
 
@@ -1233,6 +1236,7 @@ static void close_func(LexState *ls)
   GCproto *pt = fs->pt;
   BCIns *bc;
   GCRef *uvname;
+  BCLine *lineinfo;
   removevars(ls, 0);
   finalret(fs, pt);
   bc = proto_bc(pt);
@@ -1241,7 +1245,9 @@ static void close_func(LexState *ls)
   pt->sizebc = fs->pc;
   collectk(fs, pt);
   collectuv(fs, pt);
-  lj_mem_reallocvec(L, pt->lineinfo, pt->sizelineinfo, fs->pc, BCLine);
+  lineinfo = proto_lineinfo(pt);
+  lj_mem_reallocvec(L, lineinfo, pt->sizelineinfo, fs->pc, BCLine);
+  setmref(pt->lineinfo, lineinfo);
   pt->sizelineinfo = fs->pc;
   lj_mem_reallocvec(L, pt->varinfo, pt->sizevarinfo, fs->nlocvars, VarInfo);
   pt->sizevarinfo = fs->nlocvars;
@@ -1509,7 +1515,7 @@ static void funcargs(LexState *ls, ExpDesc *e)
   }
   init_exp(e, VCALL, emitINS(fs, ins));
   e->u.s.aux = base;
-  fs->pt->lineinfo[fs->pc - 1] = line;
+  proto_lineinfo(fs->pt)[fs->pc - 1] = line;
   fs->freereg = base+1;  /* call removes function and arguments and leaves
 			    (unless changed) one result */
 }
@@ -1929,9 +1935,9 @@ static void forbody(LexState *ls, BCReg base, BCLine line, BCReg nvars,
     fixjump(fs, loop, fs->pc);
     emitABC(fs, BC_ITERC, base+3, nvars+1, 2+1);
     loopend = emitAJ(fs, BC_ITERL, base+3, NO_JMP);
-    fs->pt->lineinfo[loopend-1] = line;
+    proto_lineinfo(fs->pt)[loopend-1] = line;
   }
-  fs->pt->lineinfo[loopend] = line;  /* pretend last op starts the loop */
+  proto_lineinfo(fs->pt)[loopend] = line;  /* pretend last op starts the loop */
   fixjump(fs, loopend, loop+1);
 }
 
@@ -2091,7 +2097,7 @@ static void funcstat(LexState *ls, BCLine line)
   body(ls, &b, needself, line);
   fs = ls->fs;
   storevar(fs, &v, &b);
-  fs->pt->lineinfo[fs->pc - 1] = line;
+  proto_lineinfo(fs->pt)[fs->pc - 1] = line;
 }
 
 static void exprstat(LexState *ls)