diff --git a/backend/FwLite/MiniLcm/SyncHelpers/SimpleStringDiff.cs b/backend/FwLite/MiniLcm/SyncHelpers/SimpleStringDiff.cs
index 2708a6b23..37f9e7870 100644
--- a/backend/FwLite/MiniLcm/SyncHelpers/SimpleStringDiff.cs
+++ b/backend/FwLite/MiniLcm/SyncHelpers/SimpleStringDiff.cs
@@ -5,8 +5,8 @@ namespace MiniLcm.SyncHelpers;
 public static class SimpleStringDiff
 {
     public static IEnumerable<Operation<T>> GetStringDiff<T>(string path,
-        string before,
-        string after) where T : class
+        string? before,
+        string? after) where T : class
     {
         if (before == after) yield break;
         if (after is null) yield return new Operation<T>("remove", $"/{path}", null);