diff --git a/tests/bindings/lua/test_upb.lua b/tests/bindings/lua/test_upb.lua
index 64696a52a0..b966fcc4be 100644
--- a/tests/bindings/lua/test_upb.lua
+++ b/tests/bindings/lua/test_upb.lua
@@ -651,6 +651,20 @@ function test_foo()
   assert_equal(set.file[1].name, "google/protobuf/descriptor.proto")
 end
 
+function test_descriptor()
+  local symtab = upb.SymbolTable()
+  local file_proto = descriptor.FileDescriptorProto {
+    name = "test.proto",
+    message_type = upb.Array(descriptor.DescriptorProto, {
+      descriptor.DescriptorProto{
+        name = "ABC",
+      },
+    })
+  }
+  local file = symtab:add_file(upb.encode(file_proto))
+  assert_equal(file:symtab(), symtab)
+end
+
 function test_descriptor_error()
   local symtab = upb.SymbolTable()
   local file = descriptor.FileDescriptorProto()
diff --git a/upb/bindings/lua/def.c b/upb/bindings/lua/def.c
index ca277c8354..5a4d42c4ac 100644
--- a/upb/bindings/lua/def.c
+++ b/upb/bindings/lua/def.c
@@ -668,6 +668,13 @@ static int lupb_filedef_package(lua_State *L) {
   return 1;
 }
 
+static int lupb_filedef_symtab(lua_State *L) {
+  const upb_filedef *f = lupb_filedef_check(L, 1);
+  const upb_symtab *symtab = upb_filedef_symtab(f);
+  lupb_wrapper_pushwrapper(L, 1, symtab, LUPB_SYMTAB);
+  return 1;
+}
+
 static int lupb_filedef_syntax(lua_State *L) {
   const upb_filedef *f = lupb_filedef_check(L, 1);
   lua_pushnumber(L, upb_filedef_syntax(f));
@@ -683,6 +690,7 @@ static const struct luaL_Reg lupb_filedef_m[] = {
   {"msgcount", lupb_filedef_msgcount},
   {"name", lupb_filedef_name},
   {"package", lupb_filedef_package},
+  {"symtab", lupb_filedef_symtab},
   {"syntax", lupb_filedef_syntax},
   {NULL, NULL}
 };
@@ -761,6 +769,10 @@ static int lupb_symtab_new(lua_State *L) {
   lua_setfield(L, -2, "__mode");
   lua_setmetatable(L, -2);
 
+  /* Put the symtab itself in the cache metatable. */
+  lua_pushvalue(L, -2);
+  lua_rawsetp(L, -2, lsymtab->symtab);
+
   /* Set the cache as our userval. */
   lua_setiuservalue(L, -2, LUPB_CACHE_INDEX);
 
diff --git a/upb/def.c b/upb/def.c
index 600153e8d5..4ba553a69c 100644
--- a/upb/def.c
+++ b/upb/def.c
@@ -93,17 +93,18 @@ struct upb_filedef {
   const char *package;
   const char *phpprefix;
   const char *phpnamespace;
-  upb_syntax_t syntax;
 
   const upb_filedef **deps;
   const upb_msgdef *msgs;
   const upb_enumdef *enums;
   const upb_fielddef *exts;
+  const upb_symtab *symtab;
 
   int dep_count;
   int msg_count;
   int enum_count;
   int ext_count;
+  upb_syntax_t syntax;
 };
 
 struct upb_symtab {
@@ -823,6 +824,10 @@ const upb_enumdef *upb_filedef_enum(const upb_filedef *f, int i) {
   return i < 0 || i >= f->enum_count ? NULL : &f->enums[i];
 }
 
+const upb_symtab *upb_filedef_symtab(const upb_filedef *f) {
+  return f->symtab;
+}
+
 void upb_symtab_free(upb_symtab *s) {
   upb_arena_free(s->arena);
   upb_gfree(s);
@@ -2093,6 +2098,7 @@ static const upb_filedef *_upb_symtab_addfile(
   file->msg_count = 0;
   file->enum_count = 0;
   file->ext_count = 0;
+  file->symtab = s;
 
   if (UPB_UNLIKELY(UPB_SETJMP(ctx.err))) {
     UPB_ASSERT(!upb_ok(status));
diff --git a/upb/def.h b/upb/def.h
index 6b73ef5be3..7206ec0d3e 100644
--- a/upb/def.h
+++ b/upb/def.h
@@ -277,6 +277,7 @@ int upb_filedef_enumcount(const upb_filedef *f);
 const upb_filedef *upb_filedef_dep(const upb_filedef *f, int i);
 const upb_msgdef *upb_filedef_msg(const upb_filedef *f, int i);
 const upb_enumdef *upb_filedef_enum(const upb_filedef *f, int i);
+const upb_symtab *upb_filedef_symtab(const upb_filedef *f);
 
 /* upb_symtab *****************************************************************/