diff --git a/rust-proc-macros/src/lib.rs b/rust-proc-macros/src/lib.rs
index d3adddf..407c262 100644
--- a/rust-proc-macros/src/lib.rs
+++ b/rust-proc-macros/src/lib.rs
@@ -86,6 +86,8 @@ pub fn derive_disjoint_union(input: TokenStream) -> TokenStream {
 
             fn join_with(&mut self, rhs: Self) {
                 match (self, rhs) {
+                    (_, r) if r.is_bottom() => {/*do nothing because bottom is the identity element of join*/},
+                    (s, r) if s.is_bottom() => *s = r,
                     #( (#enum_name::#variant_idents(ref mut ldom), #enum_name::#variant_idents(rdom)) => ldom.join_with(rdom), )*
                     (s, _) => *s = Self::top(),
                 }
@@ -93,6 +95,8 @@ pub fn derive_disjoint_union(input: TokenStream) -> TokenStream {
 
             fn meet_with(&mut self, rhs: Self) {
                 match (self, rhs) {
+                    (_, r) if r.is_top() => {/*do nothing because top is the identity element of meet*/},
+                    (s, r) if s.is_top() => *s = r,
                     #( (#enum_name::#variant_idents(ref mut ldom), #enum_name::#variant_idents(rdom)) => ldom.meet_with(rdom), )*
                     (s, _) => *s = Self::bottom(),
                 }
diff --git a/rust/tests/datatype/disjoint_union_test.rs b/rust/tests/disjoint_union_test.rs
similarity index 81%
rename from rust/tests/datatype/disjoint_union_test.rs
rename to rust/tests/disjoint_union_test.rs
index 02c873e..8b24d8e 100644
--- a/rust/tests/datatype/disjoint_union_test.rs
+++ b/rust/tests/disjoint_union_test.rs
@@ -11,7 +11,8 @@ use sparta::datatype::AbstractDomain;
 use sparta::datatype::DisjointUnion;
 use sparta::datatype::HashSetAbstractDomain;
 
-#[derive(Clone, DisjointUnion, PartialEq, Eq)]
+#[allow(dead_code)]
+#[derive(Clone, DisjointUnion, PartialEq, Eq, Debug)]
 enum MyUnionedDomain {
     FirstCase(HashSetAbstractDomain<i32>),
     SecondCase(HashSetAbstractDomain<i64>),
@@ -119,6 +120,31 @@ fn test_meet_diff_arm() {
     assert!(met_mudom.is_bottom());
 }
 
+#[test]
+fn test_bottom_is_right_identity_of_join() {
+    let mudom = MyUnionedDomain::SecondCase([1].into_iter().collect());
+    assert_eq!(mudom.clone().join(MyUnionedDomain::bottom()), mudom.clone());
+}
+
+#[test]
+fn test_bottom_is_left_identity_of_join() {
+    let mudom = MyUnionedDomain::SecondCase([1].into_iter().collect());
+    assert_eq!(MyUnionedDomain::bottom().join(mudom.clone()), mudom);
+}
+
+#[test]
+fn test_top_is_right_identity_of_meet() {
+    let mudom = MyUnionedDomain::SecondCase([1].into_iter().collect());
+    assert_eq!(mudom.clone().meet(MyUnionedDomain::top()), mudom.clone());
+}
+
+#[test]
+fn test_top_is_left_identity_of_meet() {
+    let mudom = MyUnionedDomain::SecondCase([1].into_iter().collect());
+    assert_eq!(MyUnionedDomain::top().meet(mudom.clone()), mudom);
+}
+
+#[allow(dead_code)]
 #[derive(Clone, DisjointUnion, PartialEq, Eq)]
 enum TestGenericsDeriveTypechecks<S, T>
 where
@@ -129,6 +155,7 @@ where
     SecondCase(HashSetAbstractDomain<T>),
 }
 
+#[allow(dead_code)]
 #[derive(Clone, DisjointUnion, PartialEq, Eq)]
 enum TestGenericsDeriveForWholeDomainTypechecks<S: AbstractDomain, T>
 where