diff --git a/src/cs_ident.cc b/src/cs_ident.cc
index 73002aa..3dba1a1 100644
--- a/src/cs_ident.cc
+++ b/src/cs_ident.cc
@@ -71,8 +71,7 @@ svar_impl::svar_impl(
 alias_impl::alias_impl(
     state &cs, string_ref name, string_ref a, int fl
 ):
-    ident_impl{ident_type::ALIAS, name, fl},
-    p_initial{cs}, p_astack{&p_initial}
+    ident_impl{ident_type::ALIAS, name, fl}, p_initial{cs}
 {
     p_initial.val_s.set_str(a);
 }
@@ -80,36 +79,31 @@ alias_impl::alias_impl(
 alias_impl::alias_impl(
     state &cs, string_ref name, std::string_view a, int fl
 ):
-    ident_impl{ident_type::ALIAS, name, fl},
-    p_initial{cs}, p_astack{&p_initial}
+    ident_impl{ident_type::ALIAS, name, fl}, p_initial{cs}
 {
     p_initial.val_s.set_str(a);
 }
 
 alias_impl::alias_impl(state &cs, string_ref name, integer_type a, int fl):
-    ident_impl{ident_type::ALIAS, name, fl},
-    p_initial{cs}, p_astack{&p_initial}
+    ident_impl{ident_type::ALIAS, name, fl}, p_initial{cs}
 {
     p_initial.val_s.set_int(a);
 }
 
 alias_impl::alias_impl(state &cs, string_ref name, float_type a, int fl):
-    ident_impl{ident_type::ALIAS, name, fl},
-    p_initial{cs}, p_astack{&p_initial}
+    ident_impl{ident_type::ALIAS, name, fl}, p_initial{cs}
 {
     p_initial.val_s.set_float(a);
 }
 
 alias_impl::alias_impl(state &cs, string_ref name, int fl):
-    ident_impl{ident_type::ALIAS, name, fl},
-    p_initial{cs}, p_astack{&p_initial}
+    ident_impl{ident_type::ALIAS, name, fl}, p_initial{cs}
 {
     p_initial.val_s.set_none();
 }
 
 alias_impl::alias_impl(state &cs, string_ref name, any_value v, int fl):
-    ident_impl{ident_type::ALIAS, name, fl},
-    p_initial{cs}, p_astack{&p_initial}
+    ident_impl{ident_type::ALIAS, name, fl}, p_initial{cs}
 {
     p_initial.val_s = v;
 }
diff --git a/src/cs_ident.hh b/src/cs_ident.hh
index 7be2021..3223c7e 100644
--- a/src/cs_ident.hh
+++ b/src/cs_ident.hh
@@ -104,7 +104,6 @@ struct alias_impl: ident_impl, alias {
     alias_impl(state &cs, string_ref n, any_value v, int flags);
 
     ident_stack p_initial;
-    alias_stack p_astack;
 };
 
 struct command_impl: ident_impl, command {
diff --git a/src/cs_thread.cc b/src/cs_thread.cc
index 6d004ec..ccc3f48 100644
--- a/src/cs_thread.cc
+++ b/src/cs_thread.cc
@@ -5,7 +5,7 @@
 namespace cubescript {
 
 thread_state::thread_state(internal_state *cs):
-    vmstack{cs}, idstack{cs}, errbuf{cs}
+    vmstack{cs}, idstack{cs}, astacks{cs}, errbuf{cs}
 {
     vmstack.reserve(32);
     idstack.reserve(MAX_ARGUMENTS);
@@ -18,7 +18,11 @@ hook_func thread_state::set_hook(hook_func f) {
 }
 
 alias_stack &thread_state::get_astack(alias *a) {
-    return static_cast<alias_impl *>(a)->p_astack;
+    auto it = astacks.try_emplace(a->get_index());
+    if (it.second) {
+        it.first->second.node = &static_cast<alias_impl *>(a)->p_initial;
+    }
+    return it.first->second;
 }
 
 } /* namespace cubescript */
diff --git a/src/cs_thread.hh b/src/cs_thread.hh
index 68de1a1..e4642d9 100644
--- a/src/cs_thread.hh
+++ b/src/cs_thread.hh
@@ -14,6 +14,7 @@ namespace cubescript {
 struct codegen_state;
 
 struct thread_state {
+    using astack_allocator = std_allocator<std::pair<int const, alias_stack>>;
     /* thread call stack */
     ident_link *callstack{};
     /* the shared state pointer */
@@ -24,8 +25,12 @@ struct thread_state {
     codegen_state *cstate{};
     /* VM stack */
     valbuf<any_value> vmstack;
-    /* alias stack */
+    /* ident stack */
     valbuf<ident_stack> idstack;
+    /* per-alias stack pointer */
+    std::unordered_map<
+        int, alias_stack, std::hash<int>, std::equal_to<int>, astack_allocator
+    > astacks;
     /* per-thread storage buffer for error messages */
     charbuf errbuf;
     /* we can attach a hook to vm events */