diff --git a/third_party/nix/src/nix-daemon/nix-daemon-proto.cc b/third_party/nix/src/nix-daemon/nix-daemon-proto.cc
index 7344811ee..3740a26b8 100644
--- a/third_party/nix/src/nix-daemon/nix-daemon-proto.cc
+++ b/third_party/nix/src/nix-daemon/nix-daemon-proto.cc
@@ -1,4 +1,6 @@
+#include <google/protobuf/empty.pb.h>
 #include <google/protobuf/util/time_util.h>
+#include <grpcpp/impl/codegen/server_context.h>
 #include <grpcpp/impl/codegen/status.h>
 #include <grpcpp/impl/codegen/status_code_enum.h>
 
@@ -184,6 +186,13 @@ class WorkerServiceImpl final : public WorkerService::Service {
     return Status::OK;
   }
 
+  Status OptimiseStore(grpc::ServerContext* context,
+                       const google::protobuf::Empty* request,
+                       google::protobuf::Empty* response) override {
+    store_->optimiseStore();
+    return Status::OK;
+  }
+
   Status QueryMissing(grpc::ServerContext* context, const StorePaths* request,
                       nix::proto::QueryMissingResponse* response) override {
     std::set<Path> targets;