diff --git a/src/java/org/rapidcontext/app/model/ApiUtil.java b/src/java/org/rapidcontext/app/model/ApiUtil.java
index d1016834..4cbe1655 100644
--- a/src/java/org/rapidcontext/app/model/ApiUtil.java
+++ b/src/java/org/rapidcontext/app/model/ApiUtil.java
@@ -248,7 +248,7 @@ public static Object serialize(Path path,
             boolean hidden = opts.get("hidden", Boolean.class, false);
             return new Dict()
                 .set("type", "index")
-                .set("modified", idx.modified())
+                .set("modified", Objects.requireNonNullElse(idx.modified(), new Date()))
                 .set("paths", Array.from(idx.paths(path, hidden)));
         } else if (obj instanceof Binary) {
             Binary data = (Binary) obj;
diff --git a/src/java/org/rapidcontext/app/plugin/PluginZipStorage.java b/src/java/org/rapidcontext/app/plugin/PluginZipStorage.java
index 0fe5961c..52e6a5c3 100644
--- a/src/java/org/rapidcontext/app/plugin/PluginZipStorage.java
+++ b/src/java/org/rapidcontext/app/plugin/PluginZipStorage.java
@@ -16,6 +16,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.util.Date;
 
 import org.apache.commons.lang3.StringUtils;
 import org.rapidcontext.core.storage.Index;
@@ -53,7 +54,7 @@ public PluginZipStorage(String pluginId, File zipFile) throws IOException {
             root.removeObject(legacyPath.name());
             paths.remove(legacyPath);
             entries.remove(legacyPath);
-            Index idx = new Index();
+            Index idx = new Index(new Date());
             root.addIndex(Plugin.PATH.name());
             paths.put(Plugin.PATH, Plugin.PATH);
             entries.put(Plugin.PATH, idx);
diff --git a/src/java/org/rapidcontext/core/storage/Index.java b/src/java/org/rapidcontext/core/storage/Index.java
index 35a611a2..bade4feb 100644
--- a/src/java/org/rapidcontext/core/storage/Index.java
+++ b/src/java/org/rapidcontext/core/storage/Index.java
@@ -71,17 +71,10 @@ public static Index merge(Index one, Index two) {
         }
     }
 
-    /**
-     * Creates a new empty index modified right now.
-     */
-    public Index() {
-        this(new Date());
-    }
-
     /**
      * Creates a new empty index.
      *
-     * @param modified       the last modified date
+     * @param modified       the last modified date, or null for unknown
      */
     public Index(Date modified) {
         this.modified = modified;
@@ -121,7 +114,7 @@ public boolean isEmpty() {
     /**
      * Returns the last modified date.
      *
-     * @return the last modified date
+     * @return the last modified date, or null if unknown
      */
     public Date modified() {
         return this.modified;
diff --git a/src/java/org/rapidcontext/core/storage/MemoryStorage.java b/src/java/org/rapidcontext/core/storage/MemoryStorage.java
index 4f3991f2..759f26f4 100644
--- a/src/java/org/rapidcontext/core/storage/MemoryStorage.java
+++ b/src/java/org/rapidcontext/core/storage/MemoryStorage.java
@@ -236,13 +236,12 @@ private void remove(Path path, boolean updateParent) {
      */
     private void indexInsert(Path path) {
         Path parent = path.parent();
-        Index idx = Objects.requireNonNullElse((Index) objects.get(parent), new Index());
+        Index idx = Objects.requireNonNullElse((Index) objects.get(parent), new Index(null));
         if (path.isIndex()) {
             idx.addIndex(path.name());
         } else {
             idx.addObject(path.name());
         }
-        idx.setModified(null);
         if (!objects.containsKey(parent)) {
             objects.put(parent, idx);
             meta.put(parent, new Metadata(Index.class, parent, Path.ROOT, null));
@@ -267,7 +266,6 @@ private void indexRemove(Path path) {
         } else {
             idx.removeObject(path.name());
         }
-        idx.setModified(null);
         if (idx.isEmpty()) {
             objects.remove(parent);
             meta.remove(parent);