diff --git a/src/reader/expect_formal_arglist_xs.cpp b/src/reader/expect_formal_arglist_xs.cpp
index 0c312302..839a2f51 100644
--- a/src/reader/expect_formal_arglist_xs.cpp
+++ b/src/reader/expect_formal_arglist_xs.cpp
@@ -5,6 +5,7 @@
 
 #include "expect_formal_arglist_xs.hpp"
 #include "expect_formal_xs.hpp"
+#include "expect_symbol_xs.hpp"
 #include "xo/expression/Variable.hpp"
 #include "xo/indentlog/print/vector.hpp"
 
@@ -46,7 +47,9 @@ namespace xo {
         {
             if (farglxs_type_ == formalarglstatetype::argl_0) {
                 this->farglxs_type_ = formalarglstatetype::argl_1a;
+                /* TODO: refactor to have setup method on each exprstate */
                 p_stack->push_exprstate(expect_formal_xs::make());
+                p_stack->push_exprstate(expect_symbol_xs::expect_symbol_expression());
             } else {
                 exprstate::on_leftparen_token(tk, p_stack, p_emit_expr);
             }