diff --git a/src/librustc/middle/dead.rs b/src/librustc/middle/dead.rs
index 282b5d13e2c61..bb7a6a6ee7b72 100644
--- a/src/librustc/middle/dead.rs
+++ b/src/librustc/middle/dead.rs
@@ -166,6 +166,7 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
                     hir::ItemKind::Fn(..)
                     | hir::ItemKind::Ty(..)
                     | hir::ItemKind::Static(..)
+                    | hir::ItemKind::Existential(..)
                     | hir::ItemKind::Const(..) => {
                         intravisit::walk_item(self, &item);
                     }
diff --git a/src/test/ui/existential_types/private_unused.rs b/src/test/ui/existential_types/private_unused.rs
new file mode 100644
index 0000000000000..736d812bc0aff
--- /dev/null
+++ b/src/test/ui/existential_types/private_unused.rs
@@ -0,0 +1,13 @@
+// compile-pass
+
+#[deny(warnings)]
+
+enum Empty { }
+trait Bar<T> {}
+impl Bar<Empty> for () {}
+
+fn boo() -> impl Bar<Empty> {}
+
+fn main() {
+    boo();
+}