diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index d3f0c4787..10056f2f1 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -760,7 +760,7 @@ Path LocalStore::queryPathFromHashPart(const string & hashPart)
 
     Path prefix = storeDir + "/" + hashPart;
 
-    return retrySQLite<Path>([&]() {
+    return retrySQLite<Path>([&]() -> std::string {
         auto state(_state.lock());
 
         auto useQueryPathFromHashPart(state->stmtQueryPathFromHashPart.use()(prefix));