diff --git a/Shoko.Server/API/v3/Models/Shoko/Group.cs b/Shoko.Server/API/v3/Models/Shoko/Group.cs
index 48220f586..05443eda0 100644
--- a/Shoko.Server/API/v3/Models/Shoko/Group.cs
+++ b/Shoko.Server/API/v3/Models/Shoko/Group.cs
@@ -274,7 +274,7 @@ public CreateOrUpdateGroupBody(SVR_AnimeGroup group)
                     var unknownSeriesIDs = SeriesIDs
                         .Where(id => !seriesList.Any(series => series.AnimeSeriesID == id))
                         .ToList();
-                    throw new Exception($"Unable to get series with ids \"{string.Join("\", \"", unknownSeriesIDs)}\".");
+                    modelState.AddModelError(nameof(SeriesIDs), $"Unable to get series with ids \"{string.Join("\", \"", unknownSeriesIDs)}\".");
                 }
 
                 // Get a list of all the series across the new inputs and the existing group.