diff --git a/src/tools/rust-analyzer/crates/hir-expand/src/db.rs b/src/tools/rust-analyzer/crates/hir-expand/src/db.rs
index 7cb1b6c02075..b7df3ee2f911 100644
--- a/src/tools/rust-analyzer/crates/hir-expand/src/db.rs
+++ b/src/tools/rust-analyzer/crates/hir-expand/src/db.rs
@@ -60,6 +60,7 @@ pub trait ExpandDatabase: RootQueryDb {
     fn proc_macros_for_crate(&self, krate: Crate) -> Option<Arc<CrateProcMacros>>;
 
     #[salsa::invoke(ast_id_map)]
+    #[salsa::lru(1024)]
     fn ast_id_map(&self, file_id: HirFileId) -> Arc<AstIdMap>;
 
     #[salsa::transparent]