diff --git a/ctl/check_test.go b/ctl/check_test.go
index 56d70f97a..1b2ebd6f6 100644
--- a/ctl/check_test.go
+++ b/ctl/check_test.go
@@ -85,7 +85,7 @@ func TestCheckCommand_Run(t *testing.T) {
 	var buf bytes.Buffer
 	io.Copy(&buf, r)
 
-	if !strings.HasPrefix(err.Error(), "checking bitmap: unmarshalling: invalid roaring file") {
+	if !strings.HasPrefix(err.Error(), "checking bitmap: unmarshalling: reading roaring header:") {
 		t.Fatalf("expect error: invalid roaring file, actual: '%s'", err)
 	}
 	//	Todo: need correct roaring file for happy path
diff --git a/fragment.go b/fragment.go
index e7014aeb0..e05b42954 100644
--- a/fragment.go
+++ b/fragment.go
@@ -1424,7 +1424,8 @@ func (f *fragment) importValue(columnIDs, values []uint64, bitDepth uint) error
 func (f *fragment) importRoaringBytes(roaringBytes []byte) error {
 	f.mu.Lock()
 	defer f.mu.Unlock()
-	bm, err := roaring.UnmarshalStandardRoaring(roaringBytes)
+	bm := roaring.NewBitmap()
+	err := bm.UnmarshalBinary(roaringBytes)
 	if err != nil {
 		return err
 	}
diff --git a/roaring/roaring.go b/roaring/roaring.go
index abf36c40e..c9f832126 100644
--- a/roaring/roaring.go
+++ b/roaring/roaring.go
@@ -17,13 +17,14 @@ package roaring
 
 import (
 	"encoding/binary"
-	"errors"
 	"fmt"
 	"hash/fnv"
 	"io"
 	"math/bits"
 	"sort"
 	"unsafe"
+
+	"github.com/pkg/errors"
 )
 
 const (
@@ -614,8 +615,9 @@ func (b *Bitmap) WriteTo(w io.Writer) (n int64, err error) {
 	return n, nil
 }
 
-// UnmarshalBinary decodes b from a binary-encoded byte slice.
-func (b *Bitmap) UnmarshalBinary(data []byte) error {
+// unmarshalPilosaRoaring treats data as being encoded in Pilosa's 64 bit
+// roaring format and decodes it into b.
+func (b *Bitmap) unmarshalPilosaRoaring(data []byte) error {
 	if len(data) < headerBaseSize {
 		return errors.New("data too small")
 	}
@@ -3408,18 +3410,17 @@ func readStandardHeader(buf []byte) (size uint32, containerTyper func(index uint
 	return
 }
 
-func UnmarshalStandardRoaring(data []byte) (*Bitmap, error) {
-	b := NewBitmap()
-
+// UnmarshalBinary decodes b from a binary-encoded byte slice. data can be in
+// either standard roaring format or Pilosa's roaring format.
+func (b *Bitmap) UnmarshalBinary(data []byte) error {
 	fileMagic := uint32(binary.LittleEndian.Uint16(data[0:2]))
-	if fileMagic == magicNumber { //if pilosa roaring
-		err := b.UnmarshalBinary(data)
-		return b, err
+	if fileMagic == magicNumber { // if pilosa roaring
+		return errors.Wrap(b.unmarshalPilosaRoaring(data), "unmarshaling as pilosa roaring")
 	}
 
 	keyN, containerTyper, header, pos, err, haveRuns := readStandardHeader(data)
 	if err != nil {
-		return nil, err
+		return errors.Wrap(err, "reading roaring header")
 	}
 
 	b.Containers.Reset()
@@ -3439,7 +3440,7 @@ func UnmarshalStandardRoaring(data []byte) (*Bitmap, error) {
 	} else {
 		readOffsets(b, data, pos, keyN)
 	}
-	return b, nil
+	return nil
 }
 
 func readOffsets(b *Bitmap, data []byte, pos int, keyN uint32) (err error) {
diff --git a/roaring/roaring_internal_test.go b/roaring/roaring_internal_test.go
index 2469657d1..caea8e2c1 100644
--- a/roaring/roaring_internal_test.go
+++ b/roaring/roaring_internal_test.go
@@ -3231,7 +3231,8 @@ func runContainerFunc(f interface{}, c ...*Container) *Container {
 func TestUnmarshalStdRoaring(t *testing.T) {
 	//generated serialize image from java(clojure) with arrays
 	rbContainerWithTwoArrays, _ := hex.DecodeString("3A300000020000000000020001000000180000001E0000000100020003000100")
-	bm, er := UnmarshalStandardRoaring(rbContainerWithTwoArrays)
+	bm := NewBitmap()
+	er := bm.UnmarshalBinary(rbContainerWithTwoArrays)
 	if er != nil {
 		t.Fatalf("UnmarshalStandardRoaring %s", er)
 	}
@@ -3240,7 +3241,8 @@ func TestUnmarshalStdRoaring(t *testing.T) {
 	}
 	//generated serialize image from java(clojure) with a run and array
 	rbContainerWithRLEandArray, _ := hex.DecodeString("3B3001000100000900010000000100010009000100")
-	bm, er = UnmarshalStandardRoaring(rbContainerWithRLEandArray)
+	bm = NewBitmap()
+	er = bm.UnmarshalBinary(rbContainerWithRLEandArray)
 	if er != nil {
 		t.Fatalf("UnmarshalStandardRoaring %s", er)
 	}
@@ -3249,7 +3251,8 @@ func TestUnmarshalStdRoaring(t *testing.T) {
 	}
 	//had to use an external file because emacs was barfing on the long line :()
 	_bitmap_array_container, _ := ioutil.ReadFile("testdata/bitmapcontainer.roaringbitmap")
-	bm, er = UnmarshalStandardRoaring(_bitmap_array_container)
+	bm = NewBitmap()
+	er = bm.UnmarshalBinary(_bitmap_array_container)
 	if er != nil {
 		t.Fatalf("UnmarshalStandardRoaring %s", er)
 	}