diff --git a/data/lalr1.cc b/data/lalr1.cc
index 4eac6351..2fe8d4cb 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -520,7 +520,8 @@ do {					\
     int yyerrstatus_ = 0;
 
     /// Semantic value of the lookahead.
-    semantic_type yylval;
+    static semantic_type yyval_default;
+    semantic_type yylval = yyval_default;
     /// Location of the lookahead.
     location_type yylloc;
     /// The locations where the error started and ended.