diff --git a/src/main/java/inra/ijpb/plugins/MergeLabelsPlugin.java b/src/main/java/inra/ijpb/plugins/MergeLabelsPlugin.java
index 82d8eee2..5ae7282c 100644
--- a/src/main/java/inra/ijpb/plugins/MergeLabelsPlugin.java
+++ b/src/main/java/inra/ijpb/plugins/MergeLabelsPlugin.java
@@ -131,13 +131,13 @@ public void run(String arg)
         }
         case 1:
         {
-            int conn = imagePlus.isStack() ? 6 : 4;
+            int conn = imagePlus.hasImageStack() ? 6 : 4;
             LabelImages.mergeLabelsWithGap(imagePlus, imagePlus.getRoi(), conn, true);
             break;
         }
         case 2:
         {
-            int conn = imagePlus.isStack() ? 26 : 6;
+            int conn = imagePlus.hasImageStack() ? 26 : 6;
             LabelImages.mergeLabelsWithGap(imagePlus, imagePlus.getRoi(), conn, true);
             break;
         }