diff --git a/lib/go/camli/schema/fileread_test.go b/lib/go/camli/schema/fileread_test.go
index 5f6d9201f..efe5987ae 100644
--- a/lib/go/camli/schema/fileread_test.go
+++ b/lib/go/camli/schema/fileread_test.go
@@ -47,10 +47,37 @@ func part(blob *test.Blob, offset, size uint64) *ContentPart {
 	return &ContentPart{BlobRef: blob.BlobRef(), Size: size, Offset: offset}
 }
 
+// filePart returns a ContentPart that references a file JSON schema
+// blob made of the provided content parts.
+func filePart(cps []*ContentPart) *ContentPart {
+	m := NewCommonFilenameMap("")
+	fileSize := int64(0)
+	cpl := []ContentPart{}
+	for _, cp := range cps {
+		fileSize += int64(cp.Size)
+		cpl = append(cpl, *cp)
+	}
+	err := PopulateRegularFileMap(m, fileSize, cpl)
+	if err != nil {
+		panic(err.String())
+	}
+	json, err := MapToCamliJson(m)
+	if err != nil {
+		panic(err.String())
+	}
+	tb := &test.Blob{json}
+	testFetcher.AddBlob(tb)
+	return &ContentPart{SubBlobRef: tb.BlobRef(), Size: uint64(fileSize)}
+}
+
 func all(blob *test.Blob) *ContentPart {
 	return part(blob, 0, uint64(blob.Size()))
 }
 
+func zero(size uint64) *ContentPart {
+	return &ContentPart{Size: size}
+}
+
 func parts(parts ...*ContentPart) []*ContentPart {
 	return parts
 }
@@ -78,6 +105,7 @@ var readTests = []readTest{
 	{parts(all(blobA), all(blobB), all(blobC)), 20, "CCCCCccccc"},
 	{parts(all(blobA), all(blobB), all(blobC)), 22, "CCCccccc"},
 	{parts(part(blobA, 5, 5), part(blobB, 0, 5), part(blobC, 4, 2)), 1, "aaaaBBBBBCc"},
+	{parts(all(blobA), zero(2), all(blobB)), 5, "aaaaa\x00\x00BBBBBbbbbb"},
 }
 
 func TestReader(t *testing.T) {
diff --git a/lib/go/camli/schema/filereader.go b/lib/go/camli/schema/filereader.go
index 82c478947..80bd3e519 100644
--- a/lib/go/camli/schema/filereader.go
+++ b/lib/go/camli/schema/filereader.go
@@ -88,14 +88,18 @@ func (fr *FileReader) closeOpenBlobs() {
 	}
 }
 
-func (fr *FileReader) readerFor(br *blobref.BlobRef) (blobref.ReadSeekCloser, os.Error) {
+func (fr *FileReader) readerFor(br *blobref.BlobRef) (rsc blobref.ReadSeekCloser, err os.Error) {
 	if fr.crbr == br {
 		return fr.cr, nil
 	}
 	fr.closeOpenBlobs()
-	rsc, _, ferr := fr.fetcher.Fetch(br)
-	if ferr != nil {
-		return nil, ferr
+	if br != nil {
+		rsc, _, err = fr.fetcher.Fetch(br)
+		if err != nil {
+			return
+		}
+	} else {
+		rsc = &zeroReader{}
 	}
 	fr.crbr = br
 	fr.cr = rsc
@@ -127,8 +131,13 @@ func (fr *FileReader) Read(p []byte) (n int, err os.Error) {
 	}
 
 	br := cp.blobref()
-	if br == nil {
-		return 0, fmt.Errorf("no blobref in content part %d", fr.ci)
+	sbr := cp.subblobref()
+	if br != nil && sbr != nil {
+		return 0, fmt.Errorf("content part index %d has both blobRef and subFileBlobRef", fr.ci)
+	}
+	if sbr != nil {
+		// TODO
+		return 0, fmt.Errorf("TODO: unsupported subFileBlobRef in content part index %d", fr.ci)
 	}
 
 	rsc, ferr := fr.readerFor(br)
@@ -164,3 +173,22 @@ func minu64(a, b uint64) uint64 {
 	}
 	return b
 }
+
+type zeroReader struct {}
+
+func (*zeroReader) Read(p []byte) (int, os.Error) {
+	for i := range p {
+		p[i] = 0
+	}
+	return len(p), nil
+}
+
+func (*zeroReader) Close() os.Error {
+	return nil
+}
+
+func (*zeroReader) Seek(offset int64, whence int) (newFilePos int64, err os.Error) {
+	// Caller is ignoring our newFilePos return value.
+	return 0, nil
+}
+
diff --git a/lib/go/camli/schema/schema.go b/lib/go/camli/schema/schema.go
index a2cb1217a..bdf94e600 100644
--- a/lib/go/camli/schema/schema.go
+++ b/lib/go/camli/schema/schema.go
@@ -99,12 +99,19 @@ type ContentPart struct {
 }
 
 func (cp *ContentPart) blobref() *blobref.BlobRef {
-	if cp.BlobRef == nil {
+	if cp.BlobRef == nil && cp.BlobRefString != "" {
 		cp.BlobRef = blobref.Parse(cp.BlobRefString)
 	}
 	return cp.BlobRef
 }
 
+func (cp *ContentPart) subblobref() *blobref.BlobRef {
+	if cp.SubBlobRef == nil && cp.SubBlobRefString != "" {
+		cp.SubBlobRef = blobref.Parse(cp.SubBlobRefString)
+	}
+	return cp.SubBlobRef
+}
+
 func stringFromMixedArray(parts []interface{}) string {
 	buf := new(bytes.Buffer)
 	for _, part := range parts {