diff --git a/src/reader/parserstatemachine.cpp b/src/reader/parserstatemachine.cpp
index 9a7ce55d..2e2abd2c 100644
--- a/src/reader/parserstatemachine.cpp
+++ b/src/reader/parserstatemachine.cpp
@@ -32,11 +32,19 @@ namespace xo {
 
         void
         parserstatemachine::push_envframe(envframe x) {
+            constexpr bool c_debug_flag = true;
+            scope log(XO_DEBUG(c_debug_flag));
+
+            log && log(xtag("frame", x));
+
             p_env_stack_->push_envframe(std::move(x));
         }
 
         void
         parserstatemachine::pop_envframe() {
+            constexpr bool c_debug_flag = true;
+            scope log(XO_DEBUG(c_debug_flag));
+
             p_env_stack_->pop_envframe();
         }
     } /*namespace scm*/
diff --git a/src/reader/sequence_xs.cpp b/src/reader/sequence_xs.cpp
index c9ee71f3..97aa0955 100644
--- a/src/reader/sequence_xs.cpp
+++ b/src/reader/sequence_xs.cpp
@@ -35,6 +35,11 @@ namespace xo {
         sequence_xs::on_expr(ref::brw<Expression> expr,
                              parserstatemachine * p_psm)
         {
+             constexpr bool c_debug_flag = true;
+             scope log(XO_DEBUG(c_debug_flag));
+
+             log && log(xtag("expr", expr.promote()));
+
             /* TODO: if expr is a DefineExpr,
              *       then need to rewrite...
              *