2 files changed, 16 insertions, 2 deletions
diff --git a/src/libstore/local-binary-cache-store.cc b/src/libstore/local-binary-cache-store.cc
index b6e72b039215..2c2944938761 100644
--- a/src/libstore/local-binary-cache-store.cc
+++ b/src/libstore/local-binary-cache-store.cc
@@ -33,6 +33,20 @@ protected:
 
     std::shared_ptr<std::string> getFile(const std::string & path) override;
 
+    PathSet queryAllValidPaths() override
+    {
+        PathSet paths;
+
+        for (auto & entry : readDirectory(binaryCacheDir)) {
+            if (entry.name.size() != 40 ||
+                !hasSuffix(entry.name, ".narinfo"))
+                continue;
+            paths.insert(settings.nixStore + "/" + entry.name.substr(0, entry.name.size() - 8));
+        }
+
+        return paths;
+    }
+
 };
 
 void LocalBinaryCacheStore::init()
diff --git a/src/libstore/s3-binary-cache-store.cc b/src/libstore/s3-binary-cache-store.cc
index 58ee0b6384b1..cffcb1bf214f 100644
--- a/src/libstore/s3-binary-cache-store.cc
+++ b/src/libstore/s3-binary-cache-store.cc
@@ -227,8 +227,8 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
 
             for (auto object : contents) {
                 auto & key = object.GetKey();
-                if (!hasSuffix(key, ".narinfo")) continue;
-                paths.insert(settings.nixStore + "/" + std::string(key, 0, key.size() - 8));
+                if (key.size() != 40 || !hasSuffix(key, ".narinfo")) continue;
+                paths.insert(settings.nixStore + "/" + key.substr(0, key.size() - 8));
             }
 
             marker = res.GetNextMarker();