diff --git a/include/xo/reader/lambda_xs.hpp b/include/xo/reader/lambda_xs.hpp
index 1152406a..e1880039 100644
--- a/include/xo/reader/lambda_xs.hpp
+++ b/include/xo/reader/lambda_xs.hpp
@@ -40,7 +40,7 @@ namespace xo {
         public:
             lambda_xs();
 
-            static std::unique_ptr<lambda_xs> make();
+            static void start(exprstatestack * p_stack, rp<Expression> * p_emit_expr);
 
             virtual void on_lambda_token(const token_type & tk,
                                          exprstatestack * p_stack,
@@ -55,6 +55,9 @@ namespace xo {
                                             exprstatestack * p_stack,
                                             rp<Expression> * p_emit_expr) override;
 
+        private:
+            static std::unique_ptr<lambda_xs> make();
+
         private:
             /** parsing state-machine state **/
             lambdastatetype lmxs_type_ = lambdastatetype::lm_0;
diff --git a/src/reader/expect_expr_xs.cpp b/src/reader/expect_expr_xs.cpp
index c91205d0..9f27d2a0 100644
--- a/src/reader/expect_expr_xs.cpp
+++ b/src/reader/expect_expr_xs.cpp
@@ -31,7 +31,7 @@ namespace xo {
         {}
 
         void
-        expect_expr_xs::on_lambda_token(const token_type & tk,
+        expect_expr_xs::on_lambda_token(const token_type & /*tk*/,
                                         exprstatestack * p_stack,
                                         rp<Expression> * p_emit_expr)
         {
@@ -41,8 +41,8 @@ namespace xo {
             //constexpr const char * self_name = "exprstate::on_leftparen";
 
             /* push lparen_0 to remember to look for subsequent rightparen. */
-            p_stack->push_exprstate(lambda_xs::make());
-            p_stack->top_exprstate().on_lambda_token(tk, p_stack, p_emit_expr);
+            lambda_xs::start(p_stack, p_emit_expr);
+            //p_stack->top_exprstate().on_lambda_token(tk, p_stack, p_emit_expr);
             //p_stack->push_exprstate(expect_expr_xs::expect_rhs_expression());
         }
 
diff --git a/src/reader/lambda_xs.cpp b/src/reader/lambda_xs.cpp
index c9c131ac..1b28cf11 100644
--- a/src/reader/lambda_xs.cpp
+++ b/src/reader/lambda_xs.cpp
@@ -14,6 +14,15 @@ namespace xo {
             return std::make_unique<lambda_xs>(lambda_xs());
         }
 
+        void
+        lambda_xs::start(exprstatestack * p_stack,
+                         rp<Expression> * p_emit_expr)
+        {
+            p_stack->push_exprstate(lambda_xs::make());
+            p_stack->top_exprstate()
+                .on_lambda_token(token_type::lambda(), p_stack, p_emit_expr);
+        }
+
         lambda_xs::lambda_xs() : exprstate(exprstatetype::lambdaexpr) {}
 
         void