diff --git a/src/main/scala/leon/purescala/Trees.scala b/src/main/scala/leon/purescala/Trees.scala
index 9261a423e54dad5fc997c9d2be8b9d8123d372b9..27db954ea660fc227290c1e27e9ee7d70e9effe7 100644
--- a/src/main/scala/leon/purescala/Trees.scala
+++ b/src/main/scala/leon/purescala/Trees.scala
@@ -181,7 +181,7 @@ object Trees {
       if(and == null) None else Some(and.exprs)
   }
 
-  class And(val exprs: Seq[Expr]) extends Expr with FixedType {
+  class And private (val exprs: Seq[Expr]) extends Expr with FixedType {
     val fixedType = BooleanType
   }