diff --git a/include/xo/reader/define_xs.hpp b/include/xo/reader/define_xs.hpp
index 10d53459..dafafed4 100644
--- a/include/xo/reader/define_xs.hpp
+++ b/include/xo/reader/define_xs.hpp
@@ -42,7 +42,9 @@ namespace xo {
 
             defexprstatetype defxs_type() const { return defxs_type_; }
 
+#ifdef OBSOLETE
             virtual bool admits_definition() const override;
+#endif
             virtual bool admits_symbol() const override;
             virtual bool admits_colon() const override;
             virtual bool admits_semicolon() const override;
diff --git a/include/xo/reader/exprseq_xs.hpp b/include/xo/reader/exprseq_xs.hpp
index 28a17088..261cbd5a 100644
--- a/include/xo/reader/exprseq_xs.hpp
+++ b/include/xo/reader/exprseq_xs.hpp
@@ -15,6 +15,11 @@ namespace xo {
          *
          **/
         class exprseq_xs : public exprstate {
+        public:
+            exprseq_xs();
+
+            static std::unique_ptr<exprseq_xs> expect_toplevel_expression_sequence();
+
         public:
             // ----- token input methods -----
 
diff --git a/include/xo/reader/exprstate.hpp b/include/xo/reader/exprstate.hpp
index c775a5b9..7b590f48 100644
--- a/include/xo/reader/exprstate.hpp
+++ b/include/xo/reader/exprstate.hpp
@@ -70,9 +70,11 @@ namespace xo {
                 {}
             virtual ~exprstate() = default;
 
+#ifdef RELOCATED
             static std::unique_ptr<exprstate> expect_toplevel_expression_sequence() {
                 return std::make_unique<exprstate>(exprstate(exprstatetype::expect_toplevel_expression_sequence));
             }
+#endif
             static std::unique_ptr<exprstate> expect_rhs_expression() {
                 return std::make_unique<exprstate>(exprstate(exprstatetype::expect_rhs_expression));
             }
@@ -85,10 +87,12 @@ namespace xo {
 
             exprstatetype exs_type() const { return exs_type_; }
 
+#ifdef OBSOLETE
             /** true iff this parsing state admits a 'def' keyword
              *  as next token
              **/
             virtual bool admits_definition() const;
+#endif
             /** true iff this parsing state admits a symbol as next token **/
             virtual bool admits_symbol() const;
             /** true iff this parsing state admits a colon as next token **/
diff --git a/include/xo/reader/paren_xs.hpp b/include/xo/reader/paren_xs.hpp
index 5992837a..670a62c3 100644
--- a/include/xo/reader/paren_xs.hpp
+++ b/include/xo/reader/paren_xs.hpp
@@ -31,7 +31,9 @@ namespace xo {
 
             static std::unique_ptr<paren_xs> lparen_0();
 
+#ifdef OBSOLETE
             virtual bool admits_definition() const override;
+#endif
             virtual bool admits_symbol() const override;
             virtual bool admits_colon() const override;
             virtual bool admits_semicolon() const override;
diff --git a/include/xo/reader/progress_xs.hpp b/include/xo/reader/progress_xs.hpp
index 0a0516cf..9df42717 100644
--- a/include/xo/reader/progress_xs.hpp
+++ b/include/xo/reader/progress_xs.hpp
@@ -22,7 +22,9 @@ namespace xo {
 
             static std::unique_ptr<progress_xs> make(rp<Expression> valex);
 
+#ifdef OBSOLETE
             virtual bool admits_definition() const override;
+#endif
             virtual bool admits_symbol() const override;
             virtual bool admits_colon() const override;
             virtual bool admits_semicolon() const override;
diff --git a/src/reader/define_xs.cpp b/src/reader/define_xs.cpp
index 95fde120..3d85c860 100644
--- a/src/reader/define_xs.cpp
+++ b/src/reader/define_xs.cpp
@@ -15,6 +15,7 @@ namespace xo {
               def_expr_{std::move(def_expr)}
         {}
 
+#ifdef OBSOLETE
         bool
         define_xs::admits_definition() const
         {
@@ -41,6 +42,7 @@ namespace xo {
 
             return false;
         }
+#endif
 
         bool
         define_xs::admits_symbol() const {
diff --git a/src/reader/exprseq_xs.cpp b/src/reader/exprseq_xs.cpp
index 012e9b2e..e0a5af6f 100644
--- a/src/reader/exprseq_xs.cpp
+++ b/src/reader/exprseq_xs.cpp
@@ -5,6 +5,17 @@
 
 namespace xo {
     namespace scm {
+        std::unique_ptr<exprseq_xs>
+        exprseq_xs::expect_toplevel_expression_sequence()
+        {
+            return std::make_unique<exprseq_xs>(exprseq_xs());
+        }
+
+        exprseq_xs::exprseq_xs()
+            : exprstate(exprstatetype::expect_toplevel_expression_sequence)
+        {
+        }
+
         void
         exprseq_xs::on_def_token(const token_type & /*tk*/,
                                  exprstatestack * p_stack)
@@ -29,5 +40,4 @@ namespace xo {
     } /*namespace scm*/
 } /*namespace xo*/
 
-
 /* end exprseq_xs.cpp */
diff --git a/src/reader/exprstate.cpp b/src/reader/exprstate.cpp
index 6116b349..b04aa227 100644
--- a/src/reader/exprstate.cpp
+++ b/src/reader/exprstate.cpp
@@ -323,8 +323,11 @@ namespace xo {
 
         void
         exprstate::on_def_token(const token_type & tk,
-                                exprstatestack * p_stack)
+                                exprstatestack * /*p_stack*/)
         {
+            this->illegal_input_error("exprstate::on_def_token", tk);
+
+#ifdef OBSOLETE
             constexpr bool c_debug_flag = true;
             scope log(XO_DEBUG(c_debug_flag));
 
@@ -347,6 +350,7 @@ namespace xo {
              *   def pi : f64 = 3.14159265
              *   def sq(x : f64) -> f64 { (x * x) }
              */
+#endif
         }
 
         void
diff --git a/src/reader/paren_xs.cpp b/src/reader/paren_xs.cpp
index 6d464178..0911928d 100644
--- a/src/reader/paren_xs.cpp
+++ b/src/reader/paren_xs.cpp
@@ -14,8 +14,10 @@ namespace xo {
             return std::make_unique<paren_xs>(paren_xs());
         }
 
+#ifdef OBSOLETE
         bool
         paren_xs::admits_definition() const { return false; }
+#endif
 
         bool
         paren_xs::admits_symbol() const { return true; }
diff --git a/src/reader/parser.cpp b/src/reader/parser.cpp
index f056eeac..5ac71dd0 100644
--- a/src/reader/parser.cpp
+++ b/src/reader/parser.cpp
@@ -5,6 +5,7 @@
 
 #include "parser.hpp"
 #include "define_xs.hpp"
+#include "exprseq_xs.hpp"
 #include "xo/expression/DefineExpr.hpp"
 #include "xo/expression/Constant.hpp"
 #include "xo/expression/ConvertExpr.hpp"
@@ -30,7 +31,7 @@ namespace xo {
         void
         parser::begin_translation_unit() {
             xs_stack_.push_exprstate
-                (exprstate::expect_toplevel_expression_sequence());
+                (exprseq_xs::expect_toplevel_expression_sequence());
         }
 
         rp<Expression>
diff --git a/src/reader/progress_xs.cpp b/src/reader/progress_xs.cpp
index a355229e..baf4df55 100644
--- a/src/reader/progress_xs.cpp
+++ b/src/reader/progress_xs.cpp
@@ -14,8 +14,10 @@ namespace xo {
               gen_expr_{std::move(valex)}
         {}
 
+#ifdef OBSOLETE
         bool
         progress_xs::admits_definition() const { return false; }
+#endif
 
         bool
         progress_xs::admits_symbol() const { return false; }