diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 5d9e96441..b0f6709aa 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -480,7 +480,7 @@ int LocalStore::getSchema()
 
 void LocalStore::openDB(State & state, bool create)
 {
-    if (access(dbDir.c_str(), R_OK | W_OK))
+    if (access(dbDir.c_str(), R_OK | (readOnly ? 0 : W_OK)))
         throw SysError("Nix database directory '%1%' is not writable", dbDir);
 
     /* Open the Nix database. */