diff --git a/liberty/LibertyParse.yy b/liberty/LibertyParse.yy
index 822ac4ad..2acde50a 100644
--- a/liberty/LibertyParse.yy
+++ b/liberty/LibertyParse.yy
@@ -41,8 +41,8 @@ int LibertyLex_lex();
   sta::LibertyStmt *stmt;
 }
 
-%left '+' '|'
-%left '*' '&'
+%left '+' '-' '|'
+%left '*' '/' '&'
 %left '^'
 %left '!'
 
@@ -56,6 +56,8 @@ int LibertyLex_lex();
 %type <line> line
 %type <ch> expr_op volt_op
 
+%expect 2
+
 %start file
 
 %{