1 files changed, 1 insertions, 1 deletions
diff --git a/src/expr.h b/src/expr.h
index 645b5cf9..798e5bec 100644
--- a/src/expr.h
+++ b/src/expr.h
@@ -107,7 +107,7 @@ public:
   virtual void    print(std::ostream& out) const;
   virtual void    dump(std::ostream& out) const;
 
-#if defined(HAVE_BOOST_SERIALIZATION)
+#if HAVE_BOOST_SERIALIZATION
 private:
   /** Serialization. */