diff --git a/doc/security-model.md b/doc/security-model.md
index 5979db53c..d09d05472 100644
--- a/doc/security-model.md
+++ b/doc/security-model.md
@@ -409,13 +409,6 @@ creating additional hardware binding:
 │  │  → Changing kernel modules or LUKS headers requires resealing DUK    │  │
 │  └─────────────────────────────────────────────────────────────────────┘  │
 │                                                                             │
-│  ┌─────────────────────────────────────────────────────────────────────┐  │
-│  │  PCR 16 (Scratch)                                                   │  │
-│  │                                                                      │  │
-│  │  Used internally for calcfuturepcr (pre-computing future values)   │  │
-│  │  Not part of any sealing policy - purely for calculation             │  │
-│  └─────────────────────────────────────────────────────────────────────┘  │
-│                                                                             │
 └─────────────────────────────────────────────────────────────────────────────┘
 ```
 
diff --git a/doc/tpm.md b/doc/tpm.md
index 8cecfb55b..8cc2ccf77 100644
--- a/doc/tpm.md
+++ b/doc/tpm.md
@@ -164,7 +164,6 @@ unchanged; the TXT mechanism adds the DRTM capability on top of it.
 | 5 | Heads `insmod` wrapper | Each loaded kernel module: parameters + binary content (default `MODULE_PCR=5`) |
 | 6 | Heads `qubes-measure-luks.sh` | LUKS header dump for each encrypted drive |
 | 7 | Heads `cbfs-init.sh`, `uefi-init.sh` | Each CBFS/UEFI file: filename then content (default `CONFIG_PCR=7`) — covers `config.user`, GPG keyring, user CBFS files |
-| 16 | `tpmr.sh calcfuturepcr` (scratch use only) | Resettable debug PCR used as scratch pad during pre-computation of future PCR values; not part of any sealing policy |
 
 PCRs 0-3 are read at seal time and included in sealing policies. The zero
 state of PCRs 0, 1, and 3 is intentional — any unexpected extension of those
diff --git a/initrd/bin/kexec-seal-key.sh b/initrd/bin/kexec-seal-key.sh
index 9c2674b8d..ce19c3e33 100755
--- a/initrd/bin/kexec-seal-key.sh
+++ b/initrd/bin/kexec-seal-key.sh
@@ -269,10 +269,8 @@ for dev in $key_devices; do
 	STATUS_OK "$dev: LUKS TPM Disk Unlock Key added to slot $duk_keyslot"
 done
 
-# Now that we have setup the new keys, measure the PCRs
-# We don't care what ends up in PCR 6; we just want
-# to get the /tmp/luksDump.txt file.  We use PCR16
-# since it should still be zero
+# Now that we have setup the new keys, measure the LUKS headers into PCR 6.
+# The dump goes to /tmp/luksDump.txt for calcfuturepcr to use as input.
 STATUS "Measuring TPM Disk Unlock Key (DUK) for sealing policy (PCR[6])"
 echo "$key_devices" | xargs /bin/qubes-measure-luks.sh ||
 	DIE "Unable to measure the LUKS headers"