diff --git a/src/lib_jit.c b/src/lib_jit.c
index 818b8787..31b27ccb 100644
--- a/src/lib_jit.c
+++ b/src/lib_jit.c
@@ -191,7 +191,7 @@ LJLIB_CF(jit_util_funcinfo)
     setintfield(L, t, "upvalues", (int32_t)pt->sizeuv);
     if (pc < pt->sizebc)
       setintfield(L, t, "currentline", lj_debug_line(pt, pc));
-    lua_pushboolean(L, (pt->flags & PROTO_IS_VARARG));
+    lua_pushboolean(L, (pt->flags & PROTO_VARARG));
     lua_setfield(L, -2, "isvararg");
     setstrV(L, L->top++, proto_chunkname(pt));
     lua_setfield(L, -2, "source");
diff --git a/src/lj_dispatch.c b/src/lj_dispatch.c
index 5fbc112c..c29cad46 100644
--- a/src/lj_dispatch.c
+++ b/src/lj_dispatch.c
@@ -172,11 +172,11 @@ void lj_dispatch_update(global_State *g)
 static void setptmode(global_State *g, GCproto *pt, int mode)
 {
   if ((mode & LUAJIT_MODE_ON)) {  /* (Re-)enable JIT compilation. */
-    pt->flags &= ~PROTO_NO_JIT;
+    pt->flags &= ~PROTO_NOJIT;
     lj_trace_reenableproto(pt);  /* Unpatch all ILOOP etc. bytecodes. */
   } else {  /* Flush and/or disable JIT compilation. */
     if (!(mode & LUAJIT_MODE_FLUSH))
-      pt->flags |= PROTO_NO_JIT;
+      pt->flags |= PROTO_NOJIT;
     lj_trace_flushproto(g, pt);  /* Flush all traces of prototype. */
   }
 }
@@ -185,6 +185,7 @@ static void setptmode(global_State *g, GCproto *pt, int mode)
 static void setptmode_all(global_State *g, GCproto *pt, int mode)
 {
   ptrdiff_t i;
+  if (!(pt->flags & PROTO_CHILD)) return;
   for (i = -(ptrdiff_t)pt->sizekgc; i < 0; i++) {
     GCobj *o = proto_kgc(pt, i);
     if (o->gch.gct == ~LJ_TPROTO) {
@@ -400,7 +401,7 @@ static int call_init(lua_State *L, GCfunc *fn)
     int numparams = pt->numparams;
     int gotparams = (int)(L->top - L->base);
     int need = pt->framesize;
-    if ((pt->flags & PROTO_IS_VARARG)) need += 1+gotparams;
+    if ((pt->flags & PROTO_VARARG)) need += 1+gotparams;
     lj_state_checkstack(L, (MSize)need);
     numparams -= gotparams;
     return numparams >= 0 ? numparams : 0;
diff --git a/src/lj_obj.h b/src/lj_obj.h
index e85cf703..3442dc0c 100644
--- a/src/lj_obj.h
+++ b/src/lj_obj.h
@@ -309,12 +309,15 @@ typedef struct GCproto {
   MRef varinfo;		/* Names and compressed extents of local variables. */
 } GCproto;
 
-#define PROTO_IS_VARARG		0x01
-#define PROTO_HAS_FNEW		0x02
-#define PROTO_HAS_RETURN	0x04
-#define PROTO_FIXUP_RETURN	0x08
-#define PROTO_NO_JIT		0x10
-#define PROTO_HAS_ILOOP		0x20
+/* Flags for prototype. */
+#define PROTO_VARARG		0x01	/* Vararg function. */
+#define PROTO_CHILD		0x02	/* Has child prototypes. */
+#define PROTO_NOJIT		0x04	/* JIT disabled for this function. */
+#define PROTO_ILOOP		0x08	/* Patched bytecode with ILOOP etc. */
+#define PROTO_FFI		0x10	/* Uses BC_KCDATA for FFI datatypes. */
+/* Only used during parsing. */
+#define PROTO_HAS_RETURN	0x20	/* Already emitted a return. */
+#define PROTO_FIXUP_RETURN	0x40	/* Need to fixup emitted returns. */
 
 #define proto_kgc(pt, idx) \
   check_exp((uintptr_t)(intptr_t)(idx) >= (uintptr_t)-(intptr_t)(pt)->sizekgc, \
diff --git a/src/lj_parse.c b/src/lj_parse.c
index bd9d9a7a..f0bb4419 100644
--- a/src/lj_parse.c
+++ b/src/lj_parse.c
@@ -513,6 +513,7 @@ static void expr_toreg_nobranch(FuncState *fs, ExpDesc *e, BCReg reg)
       ins = BCINS_AD(BC_KNUM, reg, const_num(fs, e));
 #if LJ_HASFFI
   } else if (e->k == VKCDATA) {
+    fs->flags |= PROTO_FFI;
     ins = BCINS_AD(BC_KCDATA, reg,
 		   const_gc(fs, obj2gco(cdataV(&e->u.nval)), LJ_TCDATA));
 #endif
@@ -1120,7 +1121,7 @@ static void fs_fixup_bc(FuncState *fs, GCproto *pt, BCIns *bc, MSize n)
   BCInsLine *base = fs->bcbase;
   MSize i;
   pt->sizebc = n;
-  bc[0] = BCINS_AD((fs->flags & PROTO_IS_VARARG) ? BC_FUNCV : BC_FUNCF,
+  bc[0] = BCINS_AD((fs->flags & PROTO_VARARG) ? BC_FUNCV : BC_FUNCF,
 		   fs->framesize, 0);
   for (i = 1; i < n; i++)
     bc[i] = base[i].ins;
@@ -1336,7 +1337,7 @@ static void fs_fixup_ret(FuncState *fs)
 {
   BCPos lastpc = fs->pc;
   if (lastpc <= fs->lasttarget || !bcopisret(bc_op(fs->bcbase[lastpc-1].ins))) {
-    if (fs->flags & PROTO_HAS_FNEW)
+    if (fs->flags & PROTO_CHILD)
       bcemit_AJ(fs, BC_UCLO, 0, 0);
     bcemit_AD(fs, BC_RET0, 0, 1);  /* Need final return. */
   }
@@ -1615,7 +1616,7 @@ static BCReg parse_params(LexState *ls, int needself)
 	var_new(ls, nparams++, lex_str(ls));
       } else if (ls->token == TK_dots) {
 	lj_lex_next(ls);
-	fs->flags |= PROTO_IS_VARARG;
+	fs->flags |= PROTO_VARARG;
 	break;
       } else {
 	err_syntax(ls, LJ_ERR_XPARAM);
@@ -1652,10 +1653,13 @@ static void parse_body(LexState *ls, ExpDesc *e, int needself, BCLine line)
   /* Store new prototype in the constant array of the parent. */
   expr_init(e, VRELOCABLE,
 	    bcemit_AD(pfs, BC_FNEW, 0, const_gc(pfs, obj2gco(pt), LJ_TPROTO)));
-  if (!(pfs->flags & PROTO_HAS_FNEW)) {
+#if LJ_HASFFI
+  pfs->flags |= (fs.flags & PROTO_FFI);
+#endif
+  if (!(pfs->flags & PROTO_CHILD)) {
     if (pfs->flags & PROTO_HAS_RETURN)
       pfs->flags |= PROTO_FIXUP_RETURN;
-    pfs->flags |= PROTO_HAS_FNEW;
+    pfs->flags |= PROTO_CHILD;
   }
   lj_lex_next(ls);
 }
@@ -1781,7 +1785,7 @@ static void expr_simple(LexState *ls, ExpDesc *v)
   case TK_dots: {  /* Vararg. */
     FuncState *fs = ls->fs;
     BCReg base;
-    checkcond(ls, fs->flags & PROTO_IS_VARARG, LJ_ERR_XDOTS);
+    checkcond(ls, fs->flags & PROTO_VARARG, LJ_ERR_XDOTS);
     bcreg_reserve(fs, 1);
     base = fs->freereg-1;
     expr_init(v, VCALL, bcemit_ABC(fs, BC_VARG, base, 2, fs->numparams));
@@ -2018,7 +2022,7 @@ static void parse_return(LexState *ls)
       }
     }
   }
-  if (fs->flags & PROTO_HAS_FNEW)
+  if (fs->flags & PROTO_CHILD)
     bcemit_AJ(fs, BC_UCLO, 0, 0);  /* May need to close upvalues first. */
   bcemit_INS(fs, ins);
 }
@@ -2491,7 +2495,7 @@ GCproto *lj_parse(LexState *ls)
   fs.numparams = 0;
   fs.bcbase = NULL;
   fs.bclim = 0;
-  fs.flags |= PROTO_IS_VARARG;  /* Main chunk is always a vararg func. */
+  fs.flags |= PROTO_VARARG;  /* Main chunk is always a vararg func. */
   bcemit_AD(&fs, BC_FUNCV, 0, 0);  /* Placeholder. */
   lj_lex_next(ls);  /* Read-ahead first token. */
   parse_chunk(ls);
diff --git a/src/lj_record.c b/src/lj_record.c
index fe79832a..1a18724a 100644
--- a/src/lj_record.c
+++ b/src/lj_record.c
@@ -1276,7 +1276,7 @@ static void rec_func_setup(jit_State *J)
 {
   GCproto *pt = J->pt;
   BCReg s, numparams = pt->numparams;
-  if ((pt->flags & PROTO_NO_JIT))
+  if ((pt->flags & PROTO_NOJIT))
     lj_trace_err(J, LJ_TRERR_CJITOFF);
   if (J->baseslot + pt->framesize >= LJ_MAX_JSLOTS)
     lj_trace_err(J, LJ_TRERR_STACKOV);
@@ -1292,7 +1292,7 @@ static void rec_func_vararg(jit_State *J)
 {
   GCproto *pt = J->pt;
   BCReg s, fixargs, vframe = J->maxslot+1;
-  lua_assert((pt->flags & PROTO_IS_VARARG));
+  lua_assert((pt->flags & PROTO_VARARG));
   if (J->baseslot + vframe + pt->framesize >= LJ_MAX_JSLOTS)
     lj_trace_err(J, LJ_TRERR_STACKOV);
   J->base[vframe-1] = J->base[-1];  /* Copy function up. */
diff --git a/src/lj_trace.c b/src/lj_trace.c
index fbd1b45a..2bb2075d 100644
--- a/src/lj_trace.c
+++ b/src/lj_trace.c
@@ -163,10 +163,10 @@ void LJ_FASTCALL lj_trace_free(global_State *g, GCtrace *T)
 /* Re-enable compiling a prototype by unpatching any modified bytecode. */
 void lj_trace_reenableproto(GCproto *pt)
 {
-  if ((pt->flags & PROTO_HAS_ILOOP)) {
+  if ((pt->flags & PROTO_ILOOP)) {
     BCIns *bc = proto_bc(pt);
     BCPos i, sizebc = pt->sizebc;;
-    pt->flags &= ~PROTO_HAS_ILOOP;
+    pt->flags &= ~PROTO_ILOOP;
     if (bc_op(bc[0]) == BC_IFUNCF)
       setbc_op(&bc[0], BC_FUNCF);
     for (i = 1; i < sizebc; i++) {
@@ -323,7 +323,7 @@ void lj_trace_freestate(global_State *g)
 static void blacklist_pc(GCproto *pt, BCIns *pc)
 {
   setbc_op(pc, (int)bc_op(*pc)+(int)BC_ILOOP-(int)BC_LOOP);
-  pt->flags |= PROTO_HAS_ILOOP;
+  pt->flags |= PROTO_ILOOP;
 }
 
 /* Penalize a bytecode instruction. */
@@ -359,13 +359,13 @@ static void trace_start(jit_State *J)
   lua_State *L;
   TraceNo traceno;
 
-  if ((J->pt->flags & PROTO_NO_JIT)) {  /* JIT disabled for this proto? */
+  if ((J->pt->flags & PROTO_NOJIT)) {  /* JIT disabled for this proto? */
     if (J->parent == 0) {
       /* Lazy bytecode patching to disable hotcount events. */
       lua_assert(bc_op(*J->pc) == BC_FORL || bc_op(*J->pc) == BC_ITERL ||
 		 bc_op(*J->pc) == BC_LOOP || bc_op(*J->pc) == BC_FUNCF);
       setbc_op(J->pc, (int)bc_op(*J->pc)+(int)BC_ILOOP-(int)BC_LOOP);
-      J->pt->flags |= PROTO_HAS_ILOOP;
+      J->pt->flags |= PROTO_ILOOP;
     }
     J->state = LJ_TRACE_IDLE;  /* Silently ignored. */
     return;