diff --git a/compiler/rustc_type_ir/src/outlives.rs b/compiler/rustc_type_ir/src/outlives.rs
index bfcea6a81d31..e8afaf1a4809 100644
--- a/compiler/rustc_type_ir/src/outlives.rs
+++ b/compiler/rustc_type_ir/src/outlives.rs
@@ -68,6 +68,9 @@ struct OutlivesCollector<'a, I: Interner> {
 }
 
 impl<I: Interner> TypeVisitor<I> for OutlivesCollector<'_, I> {
+    #[cfg(not(feature = "nightly"))]
+    type Result = ();
+
     fn visit_ty(&mut self, ty: I::Ty) -> Self::Result {
         if !self.visited.insert(ty) {
             return;