$ export GNUPGHOME=$HOME/gpgkey0
$ mkdir $HOME/gpgkey0
$ gpg --import keys-00000000.asc
gpg: WARNING: unsafe permissions on homedir '/home/steven/gpgkey0'
gpg: keybox '/home/steven/gpgkey0/pubring.kbx' created
gpg: /home/steven/gpgkey0/trustdb.gpg: trustdb created
gpg: key 245A210A00000000: public key "key test <keytest@example.com>" imported
gpg: key 245A210A00000000: "key test <keytest@example.com>" not changed
gpg: key 245A210A00000000: secret key imported
gpg: Total number processed: 2
gpg:               imported: 1
gpg:              unchanged: 1
gpg:       secret keys read: 1
gpg:   secret keys imported: 1

$ gpg --edit-key 245A210A00000000
gpg: WARNING: unsafe permissions on homedir '/home/steven/gpgkey0'
gpg (GnuPG) 2.1.15; Copyright (C) 2016 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Secret key is available.

sec  rsa4096/245A210A00000000
     created: 2016-09-18  expires: never       usage: SCEA
     trust: unknown       validity: unknown
[ unknown] (1). key test <keytest@example.com>

gpg> trust
sec  rsa4096/245A210A00000000
     created: 2016-09-18  expires: never       usage: SCEA
     trust: unknown       validity: unknown
[ unknown] (1). key test <keytest@example.com>

Please decide how far you trust this user to correctly verify other users' keys
(by looking at passports, checking fingerprints from different sources, etc.)

  1 = I don't know or won't say
  2 = I do NOT trust
  3 = I trust marginally
  4 = I trust fully
  5 = I trust ultimately
  m = back to the main menu

Your decision? 5
Do you really want to set this key to ultimate trust? (y/N) y

sec  rsa4096/245A210A00000000
     created: 2016-09-18  expires: never       usage: SCEA
     trust: ultimate      validity: unknown
[ unknown] (1). key test <keytest@example.com>
Please note that the shown key validity is not necessarily correct
unless you restart the program.

gpg> save
Key not changed so no update needed.


$ gpg --list-keys
gpg: WARNING: unsafe permissions on homedir '/home/steven/gpgkey0'
gpg: keydb_search failed: Invalid value
gpg: Oops: keyid_from_fingerprint: no pubkey
gpg: checking the trustdb
gpg: public key of ultimately trusted key 0000000000000000 not found
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
/home/steven/gpgkey0/pubring.kbx
--------------------------------
pub   rsa4096 2016-09-18 [SCEA]
      2B14EC5AAD9A9ADBBBAA7478245A210A00000000
uid           [ unknown] key test <keytest@example.com>


$ gpg --debug-level guru --edit-key 2B14EC5AAD9A9ADBBBAA7478245A210A00000000
gpg: WARNING: unsafe permissions on homedir '/home/steven/gpgkey0'
gpg (GnuPG) 2.1.15; Copyright (C) 2016 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

gpg: enabled debug flags: packet mpi crypto filter iobuf memory cache memstat 
trust hashing cardio ipc clock lookup extprog
gpg: DBG: [not enabled in the source] start
gpg: DBG: [not enabled in the source] keydb_new
gpg: DBG: [not enabled in the source] keydb_search enter
gpg: DBG: keydb_search: 1 search descriptions:
gpg: DBG: keydb_search   0: FPR20: '2B14 EC5A AD9A 9ADB BBAA  7478 245A 210A 
0000 0000'
gpg: DBG: keydb_search: searching keybox (resource 0 of 1)
gpg: DBG: keydb_search: searched keybox (resource 0 of 1) => Success
gpg: DBG: [not enabled in the source] keydb_search leave (found)
gpg: DBG: [not enabled in the source] keydb_get_keybock enter
gpg: DBG: parse_packet(iob=1): type=6 length=526 (parse.keydb.c.1173)
gpg: DBG: parse_packet(iob=1): type=13 length=30 (parse.keydb.c.1173)
gpg: DBG: parse_packet(iob=1): type=2 length=569 (parse.keydb.c.1173)
gpg: DBG: iobuf-1.0: underflow: buffer size: 1133; still buffered: 0 => space 
for 1133 bytes
gpg: DBG: [not enabled in the source] keydb_get_keyblock leave
gpg: DBG: finish_lookup: checking key 00000000 (all)(req_usage=0)
gpg: DBG:       using key 00000000
gpg: DBG: public key 245A210A00000000: timestamp: 2016-09-18 02:56:33 
(1474167393)
gpg: DBG: user id: key test <keytest@example.com>
[ snipped ]
Secret key is available.

gpg: DBG: [not enabled in the source] keydb_new
gpg: DBG: [not enabled in the source] keydb_search enter
gpg: DBG: keydb_search: 1 search descriptions:
gpg: DBG: keydb_search   0: FPR16: '2B14EC5AAD9A9ADBBBAA7478245A210A'
gpg: DBG: keydb_search: searching keybox (resource 0 of 1)
gpg: DBG: keydb_search: searched keybox (resource 0 of 1) => Invalid value
gpg: DBG: [not enabled in the source] keydb_search leave (not found)
gpg: keydb_search failed: Invalid value
gpg: Oops: keyid_from_fingerprint: no pubkey
gpg: DBG: get_keygrip for public key
gpg: DBG: keygrip= 7C 3F D1 21 A9 BF 67 3D B2 18 02 B5 B4 9B CF 96 5D D6 1E 18
gpg: DBG: chan_4 -> KEYINFO 7C3FD121A9BF673DB21802B5B49BCF965DD61E18
gpg: DBG: chan_4 <- S KEYINFO 7C3FD121A9BF673DB21802B5B49BCF965DD61E18 D - - - P 
- - -
gpg: DBG: chan_4 <- OK
sec  rsa4096/245A210A00000000
     created: 2016-09-18  expires: never       usage: SCEA
     trust: ultimate      validity: unknown
[ unknown] (1). key test <keytest@example.com>

$ git diff -U4
diff --git a/g10/trustdb.c b/g10/trustdb.c
index f5b4008..a79df3f 100644
--- a/g10/trustdb.c
+++ b/g10/trustdb.c
@@ -267,15 +267,19 @@ verify_own_keys(void)
             byte *fpr = rec.r.trust.fingerprint;
             int fprlen;
             u32 kid[2];
 
+#if 0
             /* Problem: We do only use fingerprints in the trustdb but
              * we need the keyID here to indetify the key; we can only
              * use that ugly hack to distinguish between 16 and 20
              * butes fpr - it does not work always so we better change
              * the whole validation code to only work with
              * fingerprints */
             fprlen = (!fpr[16] && !fpr[17] && !fpr[18] && !fpr[19])? 16:20;
+#else
+            fprlen = 20;
+#endif
             keyid_from_fingerprint (fpr, fprlen, kid);
             if (!add_utk (kid))
              log_info(_("key %s occurs more than once in the trustdb\n"),
                       keystr(kid));