diff --git a/lib/aiken/collection/dict.ak b/lib/aiken/collection/dict.ak
index a984e0b..835ce30 100644
--- a/lib/aiken/collection/dict.ak
+++ b/lib/aiken/collection/dict.ak
@@ -379,10 +379,7 @@ fn do_has_key(self: Pairs<ByteArray, value>, key k: ByteArray) -> Bool {
 /// dict.is_empty(dict.empty) == True
 /// ```
 pub fn is_empty(self: Dict<key, value>) -> Bool {
-  when self.inner is {
-    [] -> True
-    _ -> False
-  }
+  builtin.null_list(self.inner)
 }
 
 /// Extract all the keys present in a given `Dict`.
diff --git a/lib/aiken/collection/list.ak b/lib/aiken/collection/list.ak
index ef6a93d..ab0f461 100644
--- a/lib/aiken/collection/list.ak
+++ b/lib/aiken/collection/list.ak
@@ -205,10 +205,7 @@ pub fn head(self: List<a>) -> Option<a> {
 /// list.is_empty([1, 2, 3]) == False
 /// ```
 pub fn is_empty(self: List<a>) -> Bool {
-  when self is {
-    [] -> True
-    _ -> False
-  }
+  builtin.null_list(self)
 }
 
 /// Gets the index of an element of a list, if any. Otherwise, returns None.