diff --git a/include/xo/gc/DX1Collector.hpp b/include/xo/gc/DX1Collector.hpp
index 10b6b7f..f6ec9b2 100644
--- a/include/xo/gc/DX1Collector.hpp
+++ b/include/xo/gc/DX1Collector.hpp
@@ -91,6 +91,9 @@ namespace xo {
             /** storage for N object types requires 8*N bytes **/
             std::size_t object_types_z_ = 2*1024*1024;
 
+            /** storage for N object roots requires 8*N bytes **/
+            std::size_t object_roots_z_ = 16*1024;
+
             /** number of bits to represent generation **/
             std::uint64_t gen_bits_ = 8;
 
@@ -169,6 +172,7 @@ namespace xo {
             std::string_view name() const { return config_.name_; }
 
             const DArena * get_object_types() const noexcept { return &object_types_; }
+            const DArena * get_roots() const noexcept { return &roots_; }
             const DArena * get_space(role r, generation g) const noexcept { return space_[r][g]; }
             DArena * get_space(role r, generation g) noexcept { return space_[r][g]; }
             DArena * from_space(generation g) noexcept { return get_space(role::from_space(), g); }
@@ -308,6 +312,11 @@ namespace xo {
             /** if > 0: need gc for all generations < gc_pending_upto_ **/
             generation gc_pending_upto_;
 
+            /** (ab)using arena to get extensible list of root objects.
+             *  For each root store one address (type obj<AGCObject>*)
+             **/
+            DArena roots_;
+
             /** collector-managed memory here.
              *  - space_[1] is from-space
              *  - space_[0] is to-space
diff --git a/include/xo/gc/detail/RCollector.hpp b/include/xo/gc/detail/RCollector.hpp
index da8fc44..5e3eddb 100644
--- a/include/xo/gc/detail/RCollector.hpp
+++ b/include/xo/gc/detail/RCollector.hpp
@@ -30,10 +30,16 @@ namespace xo {
             bool is_type_installed(typeseq tseq) const noexcept { return O::iface()->is_type_installed(O::data(), tseq); }
 
             bool install_type(const AGCObject & iface) { return O::iface()->install_type(O::data(), iface); }
-            void add_gc_root_poly(obj<AGCObject> * p_root) { O::iface()->add_gc_root(O::data(), p_root); }
+            void add_gc_root_poly(obj<AGCObject> * p_root) { O::iface()->add_gc_root_poly(O::data(), p_root); }
             void request_gc(generation g) { O::iface()->request_gc(O::data(), g); }
             void forward_inplace(AGCObject * lhs_iface, void ** lhs_data) { O::iface()->forward_inplace(O::data(), lhs_iface, lhs_data); }
 
+            /** add root @p p_root **/
+            template<typename DRepr>
+            void add_gc_root(obj<AGCObject, DRepr> * p_root) {
+                O::iface()->add_gc_root_poly(O::data(), (obj<AGCObject> *)p_root);
+            }
+
             static bool _valid;
         };
 
diff --git a/src/gc/DX1Collector.cpp b/src/gc/DX1Collector.cpp
index 46ea2ac..2c86d5d 100644
--- a/src/gc/DX1Collector.cpp
+++ b/src/gc/DX1Collector.cpp
@@ -77,6 +77,13 @@ namespace xo {
                     .hugepage_z_ = page_z,
                     .store_header_flag_ = false});
 
+            roots_ = DArena::map(
+                ArenaConfig{
+                    .name_ = "x1-object-roots",
+                    .size_ = cfg.object_roots_z_,
+                    .hugepage_z_ = page_z,
+                    .store_header_flag_ = false});
+
             for (uint32_t igen = 0, ngen = cfg.n_generation_; igen < ngen; ++igen) {
                 space_storage_[0][igen] = DArena::map(cfg.arena_config_);
                 space_storage_[1][igen] = DArena::map(cfg.arena_config_);
@@ -119,7 +126,10 @@ namespace xo {
             accumulate_total_aux(const DX1Collector & d,
                                  size_t (DArena::* get_stat_fn)() const) noexcept
             {
-                size_t z = (d.object_types_.*get_stat_fn)();
+                size_t z1 = (d.object_types_.*get_stat_fn)();
+                size_t z2 = (d.roots_.*get_stat_fn)();
+
+                size_t z3 = 0;
 
                 for (role ri : role::all()) {
                     for (generation gj{0}; gj < d.config_.n_generation_; ++gj) {
@@ -127,11 +137,11 @@ namespace xo {
 
                         assert(arena);
 
-                        z += (arena->*get_stat_fn)();
+                        z3 += (arena->*get_stat_fn)();
                     }
                 }
 
-                return z;
+                return z1 + z2 + z3;
             }
         }
 
@@ -231,7 +241,12 @@ namespace xo {
         void
         DX1Collector::add_gc_root_poly(obj<AGCObject> * p_root) noexcept
         {
-            (void)p_root;
+            std::byte * mem
+                = roots_.alloc(typeseq::anon(),
+                               sizeof(obj<AGCObject>*));
+            assert(mem);
+
+            *(obj<AGCObject> **)mem = p_root;
         }
 
         void