diff --git a/src/lib/Make.deps b/src/lib/Make.deps
index 538e17039b1..50ba9c9e5ef 100644
--- a/src/lib/Make.deps
+++ b/src/lib/Make.deps
@@ -1,5 +1,6 @@
 bignum.install: fmt.install
 bufio.install: io.install os.install utf8.install
+bytes.install: utf8.install
 container/list.install:
 container/vector.install:
 crypto/aes.install: os.install
diff --git a/src/lib/Makefile b/src/lib/Makefile
index 0f76507a4c4..bdcfa0194e9 100644
--- a/src/lib/Makefile
+++ b/src/lib/Makefile
@@ -16,6 +16,7 @@ GC=6g
 DIRS=\
 	bignum\
 	bufio\
+	bytes\
 	container/list\
 	container/vector\
 	crypto/aes\
diff --git a/src/lib/bytes/bytes.go b/src/lib/bytes/bytes.go
index fe97b049584..a64b07b74fe 100644
--- a/src/lib/bytes/bytes.go
+++ b/src/lib/bytes/bytes.go
@@ -41,6 +41,15 @@ func Equal(a, b []byte) bool {
 	return true
 }
 
+// Copy copies the source to the destination, stopping when the source
+// is all transferred.  The caller must guarantee that there is enough
+// room in the destination.
+func Copy(dst, src []byte) {
+	for i, x := range src {
+		dst[i] = x
+	}
+}
+
 // Explode splits s into an array of UTF-8 sequences, one per Unicode character (still arrays of bytes).
 // Invalid UTF-8 sequences become correct encodings of U+FFF8.
 func Explode(s []byte) [][]byte {
diff --git a/src/lib/bytes/bytes_test.go b/src/lib/bytes/bytes_test.go
index 26b3fc21d0a..4e7cdfad652 100644
--- a/src/lib/bytes/bytes_test.go
+++ b/src/lib/bytes/bytes_test.go
@@ -128,3 +128,30 @@ func TestSplit(t *testing.T) {
 		}
 	}
 }
+
+type CopyTest struct {
+	a	string;
+	b	string;
+	res	string;
+}
+var copytests = []CopyTest {
+	CopyTest{ "", "", "" },
+	CopyTest{ "a", "", "a" },
+	CopyTest{ "a", "a", "a" },
+	CopyTest{ "a", "b", "b" },
+	CopyTest{ "xyz", "abc", "abc" },
+	CopyTest{ "wxyz", "abc", "abcz" },
+}
+
+func TestCopy(t *testing.T) {
+	for i := 0; i < len(copytests); i++ {
+		tt := copytests[i];
+		dst := io.StringBytes(tt.a);
+		Copy(dst, io.StringBytes(tt.b));
+		result := string(dst);
+		if result != tt.res {
+			t.Errorf(`Copy("%s", "%s") = "%s"; want "%s"`, tt.a, tt.b, result, tt.res);
+			continue;
+		}
+	}
+}