diff --git a/src/main/java/net/imagej/ops/labeling/MergeLabeling.java b/src/main/java/net/imagej/ops/labeling/MergeLabeling.java
index a2d2b1499..27ddf7310 100644
--- a/src/main/java/net/imagej/ops/labeling/MergeLabeling.java
+++ b/src/main/java/net/imagej/ops/labeling/MergeLabeling.java
@@ -92,7 +92,7 @@ public void compute(final ImgLabeling<L, I> input1,
 	{
 		if (mask != null) {
 			final IterableRegion iterable = Regions.iterable(mask);
-			final IterableInterval<LabelingType<L>> sample = Regions.sample(iterable,
+			final IterableInterval<LabelingType<L>> sample = Regions.sample(iterable.inside(),
 				output);
 			final RandomAccess<LabelingType<L>> randomAccess = input1.randomAccess();
 			final RandomAccess<LabelingType<L>> randomAccess2 = input2.randomAccess();