diff --git a/compiler/rustc_type_ir/src/fast_reject.rs b/compiler/rustc_type_ir/src/fast_reject.rs
index 11ec1f0a9fb0..34502f495500 100644
--- a/compiler/rustc_type_ir/src/fast_reject.rs
+++ b/compiler/rustc_type_ir/src/fast_reject.rs
@@ -232,6 +232,9 @@ impl<I: Interner, const INSTANTIATE_LHS_WITH_INFER: bool, const INSTANTIATE_RHS_
     }
 
     pub fn types_may_unify(self, lhs: I::Ty, rhs: I::Ty) -> bool {
+        if lhs == rhs {
+            return true;
+        }
         self.types_may_unify_inner(lhs, rhs, Self::STARTING_DEPTH)
     }