diff --git a/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs b/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
index 72c6d9e9851f..8005dd76b2a3 100644
--- a/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
@@ -145,7 +145,7 @@ pub(crate) struct RustcLintOptTyParser;
 
 impl<S: Stage> NoArgsAttributeParser<S> for RustcLintOptTyParser {
     const PATH: &[Symbol] = &[sym::rustc_lint_opt_ty];
-    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
     const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Struct)]);
     const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::RustcLintOptTy;
 }
@@ -154,7 +154,7 @@ pub(crate) struct RustcLintQueryInstabilityParser;
 
 impl<S: Stage> NoArgsAttributeParser<S> for RustcLintQueryInstabilityParser {
     const PATH: &[Symbol] = &[sym::rustc_lint_query_instability];
-    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
     const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
         Allow(Target::Fn),
         Allow(Target::Method(MethodKind::Inherent)),