diff --git a/src/lib_ffi.c b/src/lib_ffi.c
index 16fecacb..c2f73ed5 100644
--- a/src/lib_ffi.c
+++ b/src/lib_ffi.c
@@ -194,7 +194,7 @@ LJLIB_CF(ffi_meta___eq)		LJLIB_REC(cdata_arith MM_eq)
 
 LJLIB_CF(ffi_meta___len)	LJLIB_REC(cdata_arith MM_len)
 {
-  return lj_carith_len(L);
+  return ffi_arith(L);
 }
 
 LJLIB_CF(ffi_meta___lt)		LJLIB_REC(cdata_arith MM_lt)
diff --git a/src/lj_carith.c b/src/lj_carith.c
index cb7e8db6..cf71aaf5 100644
--- a/src/lj_carith.c
+++ b/src/lj_carith.c
@@ -265,7 +265,7 @@ int lj_carith_op(lua_State *L, MMS mm)
 {
   CTState *cts = ctype_cts(L);
   CDArith ca;
-  if (carith_checkarg(L, cts, &ca)) {
+  if (carith_checkarg(L, cts, &ca) && mm != MM_len && mm != MM_concat) {
     if (carith_int64(L, cts, &ca, mm) || carith_ptr(L, cts, &ca, mm)) {
       copyTV(L, &G(L)->tmptv2, L->top-1);  /* Remember for trace recorder. */
       return 1;
@@ -274,15 +274,6 @@ int lj_carith_op(lua_State *L, MMS mm)
   return lj_carith_meta(L, cts, &ca, mm);
 }
 
-/* No built-in functionality for length of cdata. */
-int lj_carith_len(lua_State *L)
-{
-  CTState *cts = ctype_cts(L);
-  CDArith ca;
-  carith_checkarg(L, cts, &ca);
-  return lj_carith_meta(L, cts, &ca, MM_len);
-}
-
 /* -- 64 bit bit operations helpers --------------------------------------- */
 
 #if LJ_64
diff --git a/src/lj_carith.h b/src/lj_carith.h
index af6225ae..788718d9 100644
--- a/src/lj_carith.h
+++ b/src/lj_carith.h
@@ -11,7 +11,6 @@
 #if LJ_HASFFI
 
 LJ_FUNC int lj_carith_op(lua_State *L, MMS mm);
-LJ_FUNC int lj_carith_len(lua_State *L);
 
 #if LJ_32
 LJ_FUNC uint64_t lj_carith_shl64(uint64_t x, int32_t sh);
diff --git a/src/lj_crecord.c b/src/lj_crecord.c
index 6e999cc9..e50fdbf7 100644
--- a/src/lj_crecord.c
+++ b/src/lj_crecord.c
@@ -1530,8 +1530,10 @@ void LJ_FASTCALL recff_cdata_arith(jit_State *J, RecordFFData *rd)
   }
   {
     TRef tr;
-    if (!(tr = crec_arith_int64(J, sp, s, (MMS)rd->data)) &&
-	!(tr = crec_arith_ptr(J, sp, s, (MMS)rd->data)) &&
+    MMS mm = (MMS)rd->data;
+    if ((mm == MM_len || mm == MM_concat ||
+	 (!(tr = crec_arith_int64(J, sp, s, mm)) &&
+	  !(tr = crec_arith_ptr(J, sp, s, mm)))) &&
 	!(tr = crec_arith_meta(J, sp, s, cts, rd)))
       return;
     J->base[0] = tr;