diff --git a/src/main/java/eu/siacs/conversations/services/AvatarService.java b/src/main/java/eu/siacs/conversations/services/AvatarService.java
index 1125859c36c3bf49cc0533d2a5390b831607a521..70c1d4dd7744595207c98bc187fc422dda1e6f02 100644
--- a/src/main/java/eu/siacs/conversations/services/AvatarService.java
+++ b/src/main/java/eu/siacs/conversations/services/AvatarService.java
@@ -113,7 +113,7 @@ public class AvatarService {
 		if (bitmap != null) {
 			return bitmap;
 		}
-		List<MucOptions.User> users = mucOptions.getUsers();
+		final List<MucOptions.User> users = new ArrayList<>(mucOptions.getUsers());
 		int count = users.size();
 		bitmap = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888);
 		Canvas canvas = new Canvas(bitmap);