diff --git a/src/reader/expect_formal_arglist_xs.cpp b/src/reader/expect_formal_arglist_xs.cpp
index 473cfb0c..0c312302 100644
--- a/src/reader/expect_formal_arglist_xs.cpp
+++ b/src/reader/expect_formal_arglist_xs.cpp
@@ -35,7 +35,8 @@ namespace xo {
         }
 
         expect_formal_arglist_xs::expect_formal_arglist_xs()
-            : farglxs_type_{formalarglstatetype::argl_0}
+            : exprstate(exprstatetype::expect_formal_arglist),
+              farglxs_type_{formalarglstatetype::argl_0}
         {}
 
         void