diff --git a/src/crypto/rsa/pkcs1v15.go b/src/crypto/rsa/pkcs1v15.go
index 99bd32af785..2b025582f67 100644
--- a/src/crypto/rsa/pkcs1v15.go
+++ b/src/crypto/rsa/pkcs1v15.go
@@ -244,6 +244,7 @@ func nonZeroRandomBytes(s []byte, random io.Reader) (err error) {
 // precompute a prefix of the digest value that makes a valid ASN1 DER string
 // with the correct contents.
 var hashPrefixes = map[crypto.Hash][]byte{
+	crypto.MD4:        {0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x04, 0x05, 0x00, 0x04, 0x10},
 	crypto.MD5:        {0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05, 0x05, 0x00, 0x04, 0x10},
 	crypto.SHA1:       {0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14},
 	crypto.SHA224:     {0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04, 0x05, 0x00, 0x04, 0x1c},