diff --git a/src/internal/pkgbits/decoder.go b/src/internal/pkgbits/decoder.go
index 537d48d899..9c8ad446ca 100644
--- a/src/internal/pkgbits/decoder.go
+++ b/src/internal/pkgbits/decoder.go
@@ -37,6 +37,10 @@ func NewPkgDecoder(pkgPath, input string) PkgDecoder {
 
 	r := strings.NewReader(input)
 
+	var version uint32
+	assert(binary.Read(r, binary.LittleEndian, &version) == nil)
+	assert(version == 0)
+
 	assert(binary.Read(r, binary.LittleEndian, pr.elemEndsEnds[:]) == nil)
 
 	pr.elemEnds = make([]uint32, pr.elemEndsEnds[len(pr.elemEndsEnds)-1])
diff --git a/src/internal/pkgbits/encoder.go b/src/internal/pkgbits/encoder.go
index 87ef50ed8b..820c707940 100644
--- a/src/internal/pkgbits/encoder.go
+++ b/src/internal/pkgbits/encoder.go
@@ -35,6 +35,8 @@ func (pw *PkgEncoder) DumpTo(out io.Writer) {
 		assert(binary.Write(out, binary.LittleEndian, x) == nil)
 	}
 
+	writeUint32(0) // version
+
 	var sum uint32
 	for _, elems := range &pw.elems {
 		sum += uint32(len(elems))