diff --git a/src/parse/parser-driver.cc b/src/parse/parser-driver.cc
index cb5739d..2b1122f 100644
--- a/src/parse/parser-driver.cc
+++ b/src/parse/parser-driver.cc
@@ -28,6 +28,10 @@ yy::location const& ParserDriver::location() const {
     return current_location_;
 }
 
+ParserDriver::numeric_type& ParserDriver::result() {
+    return result_;
+}
+
 ParserDriver::numeric_type const& ParserDriver::result() const {
     return result_;
 }
diff --git a/src/parse/parser-driver.hh b/src/parse/parser-driver.hh
index 9262c70..5cb09de 100644
--- a/src/parse/parser-driver.hh
+++ b/src/parse/parser-driver.hh
@@ -22,6 +22,7 @@ public:
     yy::location& location();
     yy::location const& location() const;
 
+    numeric_type& result();
     numeric_type const& result() const;
 
 private: