diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index bf340846f108c..9e358ea4eba7f 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1140,6 +1140,7 @@ rustc_queries! {
     query reachable_set(_: ()) -> &'tcx LocalDefIdSet {
         arena_cache
         desc { "reachability" }
+        cache_on_disk_if { true }
     }
 
     /// Per-body `region::ScopeTree`. The `DefId` should be the owner `DefId` for the body;