diff --git a/include/xo/reader/exprseq_xs.hpp b/include/xo/reader/exprseq_xs.hpp
index e1808a15..05d0a6e3 100644
--- a/include/xo/reader/exprseq_xs.hpp
+++ b/include/xo/reader/exprseq_xs.hpp
@@ -18,7 +18,7 @@ namespace xo {
         public:
             exprseq_xs();
 
-            static void start(exprstatestack * p_stack);
+            static void start(parserstatemachine * p_psm);
 
         public:
             // ----- token input methods -----
diff --git a/src/reader/exprseq_xs.cpp b/src/reader/exprseq_xs.cpp
index 0db1a394..b934c2ef 100644
--- a/src/reader/exprseq_xs.cpp
+++ b/src/reader/exprseq_xs.cpp
@@ -15,9 +15,9 @@ namespace xo {
         }
 
         void
-        exprseq_xs::start(exprstatestack * p_stack)
+        exprseq_xs::start(parserstatemachine * p_psm)
         {
-            p_stack->push_exprstate(exprseq_xs::make());
+            p_psm->push_exprstate(exprseq_xs::make());
         }
 
         exprseq_xs::exprseq_xs()
diff --git a/src/reader/parser.cpp b/src/reader/parser.cpp
index 9c9d373e..9301f1df 100644
--- a/src/reader/parser.cpp
+++ b/src/reader/parser.cpp
@@ -31,7 +31,11 @@ namespace xo {
 
         void
         parser::begin_translation_unit() {
-            exprseq_xs::start(&xs_stack_);
+            /* note: not using emit expr here */
+            parserstatemachine psm(&xs_stack_,
+                                   nullptr /*p_emit_expr*/);
+
+            exprseq_xs::start(&psm);
         }
 
         rp<Expression>