diff --git a/xo-reader2/include/xo/reader2/ParserStateMachine.hpp b/xo-reader2/include/xo/reader2/ParserStateMachine.hpp
index c3c179ad..466e07f8 100644
--- a/xo-reader2/include/xo/reader2/ParserStateMachine.hpp
+++ b/xo-reader2/include/xo/reader2/ParserStateMachine.hpp
@@ -31,15 +31,16 @@ namespace xo {
             using DArena = xo::mm::DArena;
 
         public:
-            ParserStateMachine(const ArenaConfig & config);
+            ParserStateMachine(const ArenaConfig & config,
+                               obj<AAllocator> * expr_alloc);
 
             /** @defgroup scm-parserstatemachine-accessors accessor methods **/
             ///@{
 
             bool debug_flag() const noexcept { return debug_flag_; }
             ParserStack * stack() const noexcept { return stack_; }
+            obj<AAllocator> * expr_alloc() const noexcept { return expr_alloc_; }
             const ParserResult & result() const noexcept { return result_; }
-            obj<AAllocator> expr_alloc() const noexcept { return expr_alloc_; }
 
             /** true iff state machine is currently idle (at top-level) **/
             bool is_at_toplevel() const noexcept;
@@ -133,7 +134,7 @@ namespace xo {
              *  scenario, where top-level Expressions can be discarded
              *  once compiled.
              **/
-            obj<AAllocator> expr_alloc_;
+            obj<AAllocator> * expr_alloc_ = nullptr;
 
             /** current output from parser **/
             ParserResult result_;
diff --git a/xo-reader2/include/xo/reader2/SchematikaParser.hpp b/xo-reader2/include/xo/reader2/SchematikaParser.hpp
index 8b4688ce..7d5f36d2 100644
--- a/xo-reader2/include/xo/reader2/SchematikaParser.hpp
+++ b/xo-reader2/include/xo/reader2/SchematikaParser.hpp
@@ -8,6 +8,7 @@
 #include "ParserStateMachine.hpp"
 #include "ParserResult.hpp"
 #include <xo/tokenizer2/Token.hpp>
+#include <xo/alloc2/Allocator.hpp>
 
 namespace xo {
     namespace scm {
@@ -153,6 +154,7 @@ namespace xo {
         class SchematikaParser {
         public:
             using ArenaConfig = xo::mm::ArenaConfig;
+            using AAllocator = xo::mm::AAllocator;
             using token_type = Token;
 
         public:
@@ -160,9 +162,13 @@ namespace xo {
              *  parser is ready to receive tokens via @ref include_token
              *
              *  @p config  arena configuration for parser memory
+             *  @p expr_alloc  allocator for schematika expressions.
+             *                 Probably shared with execution.
              *  @p debug_flag  true to enable debug logging
              **/
-            SchematikaParser(const ArenaConfig & config, bool debug_flag);
+            SchematikaParser(const ArenaConfig & config,
+                             obj<AAllocator> * expr_alloc,
+                             bool debug_flag);
 
             bool debug_flag() const { return debug_flag_; }
 
diff --git a/xo-reader2/src/reader2/ParserStateMachine.cpp b/xo-reader2/src/reader2/ParserStateMachine.cpp
index 4f54a584..4756975a 100644
--- a/xo-reader2/src/reader2/ParserStateMachine.cpp
+++ b/xo-reader2/src/reader2/ParserStateMachine.cpp
@@ -16,9 +16,10 @@ namespace xo {
     using xo::facet::with_facet;
 
     namespace scm {
-        ParserStateMachine::ParserStateMachine(const ArenaConfig & config)
+        ParserStateMachine::ParserStateMachine(const ArenaConfig & config,
+                                               obj<AAllocator> * expr_alloc)
             : parser_alloc_{DArena::map(config)},
-              expr_alloc_{with_facet<AAllocator>::mkobj(&parser_alloc_)},
+              expr_alloc_{expr_alloc},
               debug_flag_{config.debug_flag_}
         {
         }
@@ -176,7 +177,9 @@ namespace xo {
                                        xtag("ssm", ssm_name),
                                        xtag("via", "ParserStateMachine::illegal_input_on_token"));
 
-            auto errmsg = DString::from_view(expr_alloc_,
+            assert(expr_alloc_);
+
+            auto errmsg = DString::from_view(*expr_alloc_,
                                              std::string_view(errmsg_string));
 
             this->capture_error(ssm_name, errmsg);
diff --git a/xo-reader2/src/reader2/SchematikaParser.cpp b/xo-reader2/src/reader2/SchematikaParser.cpp
index 2e607e77..67af915f 100644
--- a/xo-reader2/src/reader2/SchematikaParser.cpp
+++ b/xo-reader2/src/reader2/SchematikaParser.cpp
@@ -11,14 +11,17 @@
 #include <stdexcept>
 
 namespace xo {
+    using xo::mm::AAllocator;
     using xo::tostr;
     using xo::xtag;
 
     namespace scm {
         // ----- SchematikaParser -----
 
-        SchematikaParser::SchematikaParser(const ArenaConfig & config, bool debug_flag)
-            : psm_{config},
+        SchematikaParser::SchematikaParser(const ArenaConfig & config,
+                                           obj<AAllocator> * expr_alloc,
+                                           bool debug_flag)
+            : psm_{config, expr_alloc},
               debug_flag_{debug_flag}
         {
         }
@@ -35,13 +38,13 @@ namespace xo {
 
         void
         SchematikaParser::begin_interactive_session() {
-            DExprSeqState::establish_interactive(psm_.expr_alloc(), &psm_);
+            DExprSeqState::establish_interactive(*(psm_.expr_alloc()), &psm_);
 
         }
 
         void
         SchematikaParser::begin_translation_unit() {
-            DExprSeqState::establish_batch(psm_.expr_alloc(), &psm_);
+            DExprSeqState::establish_batch(*(psm_.expr_alloc()), &psm_);
         }
 
         const ParserResult &