How to handle a subkey whose self signature uses SHA256, but for which there is a revocation certificate that uses SHA1

I found a subkey whose binding signature uses SHA256, and for which there is a revocation certificate that uses SHA1. This is a problem, because the StandardPolicy doesn't consider this subkey to be rejected: instead, the StandardPolicy consider the revocation certificate to be invalid (it uses SHA1).

Public-Key Packet, old CTB, 525 bytes
    Version: 4
    Creation time: 2016-03-05 13:08:25 UTC
    Pk algo: RSA (Encrypt or Sign)
    Pk size: 4096 bits
    Fingerprint: EA7E 6B72 4BC9 FBF2 D171  EB72 6B72 0BE9 C5CF 6D9E
    KeyID: 6B72 0BE9 C5CF 6D9E
  
...
Public-Subkey Packet, old CTB, 525 bytes
    Version: 4
    Creation time: 2016-08-19 00:26:00 UTC
    Pk algo: RSA (Encrypt or Sign)
    Pk size: 4096 bits
    Fingerprint: 1B7E 3A5A 587E BEB4 B045  09F2 6109 2ABB 9741 9DF3
    KeyID: 6109 2ABB 9741 9DF3
  
Signature Packet, old CTB, 1086 bytes
    Version: 4
    Type: SubkeyBinding
    Pk algo: RSA (Encrypt or Sign)
    Hash algo: SHA256
    Hashed area:
      Signature creation time: 2016-08-19 00:26:00 UTC
      Key flags: S
    Unhashed area:
      Issuer: 6B72 0BE9 C5CF 6D9E
      Embedded signature: 
        Signature Packet
          Version: 4
          Type: PrimaryKeyBinding
          Pk algo: RSA (Encrypt or Sign)
          Hash algo: SHA256
          Hashed area:
            Signature creation time: 2016-08-19 00:26:00 UTC
          Unhashed area:
            Issuer: 6109 2ABB 9741 9DF3
          Digest prefix: F064
          Level: 0 (signature over data)
        
    Digest prefix: 1F23
    Level: 0 (signature over data)
  
Signature Packet, old CTB, 543 bytes
    Version: 4
    Type: SubkeyRevocation
    Pk algo: RSA (Encrypt or Sign)
    Hash algo: SHA1
    Hashed area:
      Signature creation time: 2017-04-26 01:40:10 UTC
      Reason for revocation: Key is superseded
    Unhashed area:
      Issuer: 6B72 0BE9 C5CF 6D9E
    Digest prefix: 3B24
    Level: 0 (signature over data)