diff --git a/bitmap.go b/bitmap.go
index eb8f7f799..72296efab 100644
--- a/bitmap.go
+++ b/bitmap.go
@@ -103,10 +103,14 @@ func (b *Bitmap) Xor(other *Bitmap) *Bitmap {
 
 	itr := newMergeSegmentIterator(b.segments, other.segments)
 	for s0, s1 := itr.next(); s0 != nil || s1 != nil; s0, s1 = itr.next() {
-		// Ignore non-overlapping segments.
-		if s0 == nil || s1 == nil {
+		if s1 == nil {
+			segments = append(segments, *s0)
+			continue
+		} else if s0 == nil {
+			segments = append(segments, *s1)
 			continue
 		}
+
 		segments = append(segments, *s0.Xor(s1))
 	}
 
diff --git a/bitmap_test.go b/bitmap_test.go
new file mode 100644
index 000000000..4fcd1b115
--- /dev/null
+++ b/bitmap_test.go
@@ -0,0 +1,92 @@
+// Copyright 2017 Pilosa Corp.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package pilosa_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/pilosa/pilosa"
+)
+
+// Ensure a bitmap can be merged
+func TestBitmap_Merge(t *testing.T) {
+	bm1 := pilosa.NewBitmap(1, 2, 3, SliceWidth+1, 2*SliceWidth)
+	bm2 := pilosa.NewBitmap(3, 4, 5)
+	bm1.Merge(bm2)
+
+	if bm1.Count() != 7 {
+		t.Fatalf("Count after merge %d != 7\n", bm1.Count())
+	}
+
+}
+
+// Ensure a bitmap can Xor'ed
+func TestBitmap_Xor(t *testing.T) {
+	bm1 := pilosa.NewBitmap(0, 1, SliceWidth)
+	bm2 := pilosa.NewBitmap(0, 2*SliceWidth)
+	exp := []uint64{1, SliceWidth, 2 * SliceWidth}
+
+	res := bm1.Xor(bm2)
+	if res.Count() != 3 {
+		t.Fatalf("Test 1 Count after xor %d != 3\n", res.Count())
+	}
+
+	if !reflect.DeepEqual(res.Bits(), exp) {
+		t.Fatalf("Test 2 Results %v != expected %v\n", res.Bits(), exp)
+	}
+	res = bm2.Xor(bm1)
+	if res.Count() != 3 {
+		t.Fatalf("Test 3 Count after xor %d != 3\n", res.Count())
+	}
+	if !reflect.DeepEqual(res.Bits(), exp) {
+		t.Fatalf("Test 4 Results %v != expected %v\n", res.Bits(), exp)
+	}
+
+}
+func TestBitmap_Union_Segment(t *testing.T) {
+	bm1 := pilosa.NewBitmap(0, 1, SliceWidth)
+	bm2 := pilosa.NewBitmap(0, 2*SliceWidth)
+	exp := []uint64{0, 1, SliceWidth, 2 * SliceWidth}
+	res := bm1.Union(bm2)
+
+	if res.Count() != 4 {
+		t.Fatalf("Test 1 Count after Union %d != 5\n", res.Count())
+	}
+	if !reflect.DeepEqual(res.Bits(), exp) {
+		t.Fatalf("Test 2 Union Results %v != expected %v\n", res.Bits(), exp)
+	}
+	res = bm2.Union(bm1)
+	if res.Count() != 4 {
+		t.Fatalf("Test 3 Count after xor %d != 5\n", res.Count())
+	}
+	if !reflect.DeepEqual(res.Bits(), exp) {
+		t.Fatalf("Test 2 Union Results %v != expected %v\n", res.Bits(), exp)
+	}
+}
+
+func TestBitmap_Difference_Segment(t *testing.T) {
+	bm1 := pilosa.NewBitmap(0, 1, SliceWidth)
+	bm2 := pilosa.NewBitmap(0, 2*SliceWidth)
+	exp := []uint64{1, SliceWidth}
+	res := bm1.Difference(bm2)
+
+	if res.Count() != 2 {
+		t.Fatalf("Test 1 Count after Difference %d != 5\n", res.Count())
+	}
+	if !reflect.DeepEqual(res.Bits(), exp) {
+		t.Fatalf("Test 2 Difference Results %v != expected %v\n", res.Bits(), exp)
+	}
+}