diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9ad501620..d3f111dbf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -36,7 +36,7 @@ All notable changes to this project will be documented in this file.
 - [GUI] Use better console hiding API (#4051 by: HebaruSan)
 - [Core] Trigger progress updates for frozen downloads (#4052 by: HebaruSan)
 - [GUI] Fix NRE on trying to update all when there's nothing to update (#4054 by: HebaruSan)
-- [Core] Tolerate null repo URLs (#4077 by: HebaruSan)
+- [Core] Fix NRE in repo update with corrupted etags.json file (#4077, #4078 by: HebaruSan)
 
 ### Internal
 
diff --git a/Core/Repositories/RepositoryDataManager.cs b/Core/Repositories/RepositoryDataManager.cs
index 4e76e8363..3baef358c 100644
--- a/Core/Repositories/RepositoryDataManager.cs
+++ b/Core/Repositories/RepositoryDataManager.cs
@@ -146,9 +146,7 @@ public UpdateResult Update(Repository[]       repos,
                                 .Where(r => r.uri != null
                                             && (r.uri.IsFile
                                                 || skipETags
-                                                || (!etags.TryGetValue(r.uri, out string etag)
-                                                    || !File.Exists(GetRepoDataPath(r))
-                                                    || etag != Net.CurrentETag(r.uri))))
+                                                || repoDataStale(r)))
                                 .ToArray();
             if (toUpdate.Length < 1)
             {
@@ -240,11 +238,15 @@ public UpdateResult Update(Repository[]       repos,
         /// </summary>
         public event Action<Repository[]> Updated;
 
+        #region ETags
+
         private void loadETags()
         {
             try
             {
-                etags = JsonConvert.DeserializeObject<Dictionary<Uri, string>>(File.ReadAllText(etagsPath));
+                etags = JsonConvert.DeserializeObject<Dictionary<Uri, string>>(File.ReadAllText(etagsPath))
+                        // An empty or all-null file can deserialize as null
+                        ?? new Dictionary<Uri, string>();
             }
             catch
             {
@@ -270,6 +272,16 @@ private void setETag(Uri url, string filename, Exception error, string etag)
             }
         }
 
+        private bool repoDataStale(Repository r)
+            // No ETag on file
+            => !etags.TryGetValue(r.uri, out string etag)
+               // No data on disk
+               || !File.Exists(GetRepoDataPath(r))
+               // Current ETag doesn't match
+               || etag != Net.CurrentETag(r.uri);
+
+        #endregion
+
         private RepositoryData GetRepoData(Repository repo)
             => repositoriesData.TryGetValue(repo, out RepositoryData data)
                 ? data