diff --git a/include/xo/reader/expect_formal_arglist_xs.hpp b/include/xo/reader/expect_formal_arglist_xs.hpp
index 501d945f..82116133 100644
--- a/include/xo/reader/expect_formal_arglist_xs.hpp
+++ b/include/xo/reader/expect_formal_arglist_xs.hpp
@@ -71,7 +71,7 @@ namespace xo {
 
         private:
             /** parsing state-machine state **/
-            formalarglstatetype farglxs_type_;
+            formalarglstatetype farglxs_type_ = formalarglstatetype::argl_0;
             /** populate with (parmaeter-name, parameter-type) list
              *  as they're encountered
              **/
diff --git a/include/xo/reader/expect_formal_xs.hpp b/include/xo/reader/expect_formal_xs.hpp
index b4c046b9..79b8bf05 100644
--- a/include/xo/reader/expect_formal_xs.hpp
+++ b/include/xo/reader/expect_formal_xs.hpp
@@ -45,7 +45,7 @@ namespace xo {
          **/
         class expect_formal_xs : public exprstate {
         public:
-            expect_formal_xs() = default;
+            expect_formal_xs();
 
             static std::unique_ptr<expect_formal_xs> make();