diff --git a/roaring/roaring.go b/roaring/roaring.go
index 9eb927d79..578547506 100644
--- a/roaring/roaring.go
+++ b/roaring/roaring.go
@@ -2481,6 +2481,7 @@ func differenceRunArray(a, b *container) *container {
 				continue
 			}
 			output.runs = append(output.runs, interval16{start: start, last: vb - 1})
+			output.n += int(vb - start)
 			start = vb + 1
 			bidx++
 			if bidx >= len(b.array) {
@@ -2491,6 +2492,7 @@ func differenceRunArray(a, b *container) *container {
 
 		if start <= run.last {
 			output.runs = append(output.runs, interval16{start: start, last: run.last})
+			output.n += int(run.last - start + 1)
 		}
 	}
 	output.Optimize()
diff --git a/roaring/roaring_internal_test.go b/roaring/roaring_internal_test.go
index 0afa346d1..bdc08b649 100644
--- a/roaring/roaring_internal_test.go
+++ b/roaring/roaring_internal_test.go
@@ -763,7 +763,7 @@ func TestDifferenceMixed(t *testing.T) {
 	res := difference(a, b)
 
 	if !reflect.DeepEqual(res.array, []uint16{5, 7, 9}) {
-		t.Fatalf("test #1 expected %v, but got %v", []uint16{5, 7, 9}, res.array)
+		t.Fatalf("test #1 expected %v, but got %#v", []uint16{5, 7, 9}, res)
 	}
 
 	res = difference(b, a)