diff --git a/include/xo/reader/define_xs.hpp b/include/xo/reader/define_xs.hpp
index 13b3d558..880dd309 100644
--- a/include/xo/reader/define_xs.hpp
+++ b/include/xo/reader/define_xs.hpp
@@ -81,6 +81,8 @@ namespace xo {
 
             virtual void on_expr(ref::brw<Expression> expr,
                                  parserstatemachine * p_psm) override;
+            virtual void on_expr_with_semicolon(ref::brw<Expression> expr,
+                                                parserstatemachine * p_psm) override;
             virtual void on_symbol(const std::string & symbol_name,
                                    parserstatemachine * p_psm) override;
             virtual void on_typedescr(TypeDescr td,
diff --git a/include/xo/reader/expect_expr_xs.hpp b/include/xo/reader/expect_expr_xs.hpp
index c3e8a513..646a803a 100644
--- a/include/xo/reader/expect_expr_xs.hpp
+++ b/include/xo/reader/expect_expr_xs.hpp
@@ -47,6 +47,12 @@ namespace xo {
             /** update exprstate in response to a successfully-parsed subexpression **/
             virtual void on_expr(ref::brw<Expression> expr,
                                  parserstatemachine * p_psm) override;
+            /** update exprstate in response to a successfully-parsed subexpression,
+             *  that's terminated by semicolon ';'
+             **/
+            virtual void on_expr_with_semicolon(ref::brw<Expression> expr,
+                                                parserstatemachine * p_psm) override;
+
 
         private:
             static std::unique_ptr<expect_expr_xs> make(bool allow_defs,
diff --git a/include/xo/reader/exprstate.hpp b/include/xo/reader/exprstate.hpp
index 8c5c9d6a..a6acad1f 100644
--- a/include/xo/reader/exprstate.hpp
+++ b/include/xo/reader/exprstate.hpp
@@ -107,6 +107,10 @@ namespace xo {
             virtual void on_expr(ref::brw<Expression> expr,
                                  parserstatemachine * p_psm);
 
+            /** update exprstate in response to a successfully-parsed subexpression, that ends with semicolon **/
+            virtual void on_expr_with_semicolon(ref::brw<Expression> expr,
+                                                parserstatemachine * p_psm);
+
             /** update exprstate when expecting a symbol **/
             virtual void on_symbol(const std::string & symbol,
                                    parserstatemachine * p_psm);
diff --git a/include/xo/reader/lambda_xs.hpp b/include/xo/reader/lambda_xs.hpp
index 79c084ab..830135a3 100644
--- a/include/xo/reader/lambda_xs.hpp
+++ b/include/xo/reader/lambda_xs.hpp
@@ -48,6 +48,8 @@ namespace xo {
                                            parserstatemachine * p_psm) override;
             virtual void on_expr(ref::brw<Expression> expr,
                                  parserstatemachine * p_psm) override;
+            virtual void on_expr_with_semicolon(ref::brw<Expression> expr,
+                                                parserstatemachine * p_psm) override;
             virtual void on_semicolon_token(const token_type & tk,
                                             parserstatemachine * p_psm) override;
 
diff --git a/include/xo/reader/parserstatemachine.hpp b/include/xo/reader/parserstatemachine.hpp
index ac3c5cd8..065513c5 100644
--- a/include/xo/reader/parserstatemachine.hpp
+++ b/include/xo/reader/parserstatemachine.hpp
@@ -45,10 +45,13 @@ namespace xo {
 
             // ----- parsing outputs -----
 
+            void on_expr(ref::brw<Expression> expr);
+            void on_expr_with_semicolon(ref::brw<Expression> expr);
             void on_symbol(const std::string & symbol);
 
             // ---- parsing inputs -----
 
+            void on_semicolon_token(const token_type & tk);
             void on_leftbrace_token(const token_type & tk);
             void on_rightbrace_token(const token_type & tk);
 
diff --git a/src/reader/define_xs.cpp b/src/reader/define_xs.cpp
index 88ddb9d3..d251652a 100644
--- a/src/reader/define_xs.cpp
+++ b/src/reader/define_xs.cpp
@@ -88,6 +88,13 @@ namespace xo {
             }
 
             exprstate::on_expr(expr, p_psm);
+        void
+        define_xs::on_expr_with_semicolon(ref::brw<Expression> expr,
+                                          parserstatemachine * p_psm)
+        {
+            this->on_expr(expr, p_psm);
+            /* semicolon is allowed to terminate def expr */
+            this->on_semicolon_token(token_type::semicolon(), p_psm);
         }
 
         void
diff --git a/src/reader/expect_expr_xs.cpp b/src/reader/expect_expr_xs.cpp
index 3fe2aacf..af27d720 100644
--- a/src/reader/expect_expr_xs.cpp
+++ b/src/reader/expect_expr_xs.cpp
@@ -195,6 +195,21 @@ namespace xo {
             p_psm->top_exprstate().on_expr(expr, p_psm);
         } /*on_expr*/
 
+        void
+        expect_expr_xs::on_expr_with_semicolon(ref::brw<Expression> expr,
+                                               parserstatemachine * p_psm)
+        {
+            constexpr bool c_debug_flag = true;
+            scope log(XO_DEBUG(c_debug_flag));
+
+            log && log(xtag("exstype", this->exs_type_),
+                       xtag("expr", expr.promote()));
+
+            std::unique_ptr<exprstate> self = p_psm->pop_exprstate();
+
+            p_psm->on_expr_with_semicolon(expr);
+        } /*on_expr_with_semicolon*/
+
     } /*namespace scm*/
 } /*namespace xo*/
 
diff --git a/src/reader/exprstate.cpp b/src/reader/exprstate.cpp
index f472b070..550e20d0 100644
--- a/src/reader/exprstate.cpp
+++ b/src/reader/exprstate.cpp
@@ -387,6 +387,19 @@ namespace xo {
             assert(false);
         } /*on_expr*/
 
+        void
+        exprstate::on_expr_with_semicolon(ref::brw<Expression> expr,
+                                          parserstatemachine * /*p_psm*/)
+        {
+            constexpr bool c_debug_flag = true;
+            scope log(XO_DEBUG(c_debug_flag));
+
+            log && log(xtag("exstype", this->exs_type_),
+                       xtag("expr", expr));
+
+            assert(false);
+        } /*on_expr_with_semicolon*/
+
         void
         exprstate::on_symbol(const std::string & symbol_name,
                              parserstatemachine * /*p_psm*/)
diff --git a/src/reader/lambda_xs.cpp b/src/reader/lambda_xs.cpp
index 00fb5c0e..8aed4511 100644
--- a/src/reader/lambda_xs.cpp
+++ b/src/reader/lambda_xs.cpp
@@ -66,6 +66,14 @@ namespace xo {
             }
         }
 
+        void
+        lambda_xs::on_expr_with_semicolon(ref::brw<Expression> expr,
+                                          parserstatemachine * p_psm)
+        {
+            this->on_expr(expr, p_psm);
+            this->on_semicolon_token(token_type::semicolon(), p_psm);
+        }
+
         void
         lambda_xs::on_semicolon_token(const token_type & tk,
                                       parserstatemachine * p_psm)
diff --git a/src/reader/parserstatemachine.cpp b/src/reader/parserstatemachine.cpp
index 9ed21d0a..44700814 100644
--- a/src/reader/parserstatemachine.cpp
+++ b/src/reader/parserstatemachine.cpp
@@ -48,6 +48,32 @@ namespace xo {
             p_env_stack_->pop_envframe();
         }
 
+        void
+        parserstatemachine::on_expr(ref::brw<Expression> x)
+        {
+            constexpr bool c_debug_flag = true;
+            scope log(XO_DEBUG(c_debug_flag));
+
+            log && log(xtag("x", x),
+                       xtag("psm", *this));
+
+            this->p_stack_
+                ->top_exprstate().on_expr(x, this);
+        }
+
+        void
+        parserstatemachine::on_expr_with_semicolon(ref::brw<Expression> x)
+        {
+            constexpr bool c_debug_flag = true;
+            scope log(XO_DEBUG(c_debug_flag));
+
+            log && log(xtag("x", x),
+                       xtag("psm", *this));
+
+            this->p_stack_
+                ->top_exprstate().on_expr_with_semicolon(x, this);
+        }
+
         void
         parserstatemachine::on_symbol(const std::string & x)
         {
diff --git a/src/reader/progress_xs.cpp b/src/reader/progress_xs.cpp
index fcb32142..d716bd0c 100644
--- a/src/reader/progress_xs.cpp
+++ b/src/reader/progress_xs.cpp
@@ -215,7 +215,7 @@ namespace xo {
         }
 
         void
-        progress_xs::on_semicolon_token(const token_type & tk,
+        progress_xs::on_semicolon_token(const token_type & /*tk*/,
                                         parserstatemachine * p_psm)
         {
             /* note: implementation parllels .on_rightparen_token() */
@@ -227,7 +227,7 @@ namespace xo {
 
             std::unique_ptr<exprstate> self = p_psm->pop_exprstate();
 
-            p_psm->top_exprstate().on_expr(expr, p_psm);
+            p_psm->on_expr_with_semicolon(expr);
 
             /* control here on input like:
              *   (1.234;