diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index 7d994359ed48b..0a1f7738632c1 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -2594,7 +2594,8 @@ impl<K: Hash, V: Hash, A: Allocator + Clone> Hash for BTreeMap<K, V, A> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<K, V> Default for BTreeMap<K, V> {
+#[rustc_const_unstable(feature = "const_default", issue = "143894")]
+const impl<K, V> Default for BTreeMap<K, V> {
     /// Creates an empty `BTreeMap`.
     fn default() -> BTreeMap<K, V> {
         BTreeMap::new()
diff --git a/tests/ui/traits/const-traits/const-traits-alloc.rs b/tests/ui/traits/const-traits/const-traits-alloc.rs
index 4dfec2f77f1ba..fe882dcf59629 100644
--- a/tests/ui/traits/const-traits/const-traits-alloc.rs
+++ b/tests/ui/traits/const-traits/const-traits-alloc.rs
@@ -5,5 +5,8 @@
 const STRING: String = Default::default();
 // alloc::vec
 const VEC: Vec<()> = Default::default();
+// alloc::collections::btree::map::BTreeMap
+use std::collections::BTreeMap;
+const BTREE: BTreeMap<(), ()> = Default::default();
 
 fn main() {}