diff --git a/lix/libstore/realisation.cc b/lix/libstore/realisation.cc
index fde768d4a..4e8c37d47 100644
--- a/lix/libstore/realisation.cc
+++ b/lix/libstore/realisation.cc
@@ -1,6 +1,7 @@
 #include "lix/libstore/realisation.hh"
 #include "lix/libstore/store-api.hh"
 #include "lix/libutil/closure.hh"
+#include "lix/libutil/result.hh"
 #include <nlohmann/json.hpp>
 
 namespace nix {
@@ -158,11 +159,11 @@ bool Realisation::isCompatibleWith(const Realisation & other) const
     return false;
 }
 
-void RealisedPath::closure(
+kj::Promise<Result<void>> RealisedPath::closure(
     Store& store,
     const RealisedPath::Set& startPaths,
     RealisedPath::Set& ret)
-{
+try {
     // FIXME: This only builds the store-path closure, not the real realisation
     // closure
     StorePathSet initialStorePaths, pathsClosure;
@@ -171,18 +172,26 @@ void RealisedPath::closure(
     store.computeFSClosure(initialStorePaths, pathsClosure);
     ret.insert(startPaths.begin(), startPaths.end());
     ret.insert(pathsClosure.begin(), pathsClosure.end());
+    co_return result::success();
+} catch (...) {
+    co_return result::current_exception();
 }
 
-void RealisedPath::closure(Store& store, RealisedPath::Set & ret) const
-{
-    RealisedPath::closure(store, {*this}, ret);
+kj::Promise<Result<void>> RealisedPath::closure(Store& store, RealisedPath::Set & ret) const
+try {
+    TRY_AWAIT(RealisedPath::closure(store, {*this}, ret));
+    co_return result::success();
+} catch (...) {
+    co_return result::current_exception();
 }
 
-RealisedPath::Set RealisedPath::closure(Store& store) const
-{
+kj::Promise<Result<RealisedPath::Set>> RealisedPath::closure(Store& store) const
+try {
     RealisedPath::Set ret;
-    closure(store, ret);
-    return ret;
+    TRY_AWAIT(closure(store, ret));
+    co_return ret;
+} catch (...) {
+    co_return result::current_exception();
 }
 
 } // namespace nix
diff --git a/lix/libstore/realisation.hh b/lix/libstore/realisation.hh
index 463b19916..02697f267 100644
--- a/lix/libstore/realisation.hh
+++ b/lix/libstore/realisation.hh
@@ -133,9 +133,9 @@ struct RealisedPath {
      */
     StorePath path() const;
 
-    void closure(Store& store, Set& ret) const;
-    static void closure(Store& store, const Set& startPaths, Set& ret);
-    Set closure(Store& store) const;
+    kj::Promise<Result<void>> closure(Store & store, Set & ret) const;
+    static kj::Promise<Result<void>> closure(Store & store, const Set & startPaths, Set & ret);
+    kj::Promise<Result<Set>> closure(Store & store) const;
 
     GENERATE_CMP(RealisedPath, me->raw);
 };
diff --git a/lix/libstore/store-api.cc b/lix/libstore/store-api.cc
index 60e927ee6..9262d6c89 100644
--- a/lix/libstore/store-api.cc
+++ b/lix/libstore/store-api.cc
@@ -1317,7 +1317,7 @@ try {
     if (&srcStore == &dstStore) co_return result::success();
 
     RealisedPath::Set closure;
-    RealisedPath::closure(srcStore, paths, closure);
+    TRY_AWAIT(RealisedPath::closure(srcStore, paths, closure));
 
     TRY_AWAIT(copyPaths(srcStore, dstStore, closure, repair, checkSigs, substitute));
     co_return result::success();