diff --git a/include/xo/reader/lambda_xs.hpp b/include/xo/reader/lambda_xs.hpp
index 4b4fb74c..1152406a 100644
--- a/include/xo/reader/lambda_xs.hpp
+++ b/include/xo/reader/lambda_xs.hpp
@@ -57,7 +57,7 @@ namespace xo {
 
         private:
             /** parsing state-machine state **/
-            lambdastatetype lmxs_type_;
+            lambdastatetype lmxs_type_ = lambdastatetype::lm_0;
 
             /** formal parameter list **/
             std::vector<rp<Variable>> argl_;
diff --git a/src/reader/lambda_xs.cpp b/src/reader/lambda_xs.cpp
index a4a19845..d6b1eec1 100644
--- a/src/reader/lambda_xs.cpp
+++ b/src/reader/lambda_xs.cpp
@@ -14,7 +14,7 @@ namespace xo {
             return std::make_unique<lambda_xs>(lambda_xs());
         }
 
-        lambda_xs::lambda_xs() {}
+        lambda_xs::lambda_xs() : exprstate(exprstatetype::lambdaexpr) {}
 
         void
         lambda_xs::on_lambda_token(const token_type & tk,