diff --git a/releases/signatures.txt b/releases/signatures.txt
index f30213be..035c1287 100644
--- a/releases/signatures.txt
+++ b/releases/signatures.txt
@@ -4,7 +4,9 @@ Hash: SHA256
 715a3ec7a91d2366788b14a243e7343de875714b647d1e2bc906ecc5b752d8d9  README.md
 8f71336a78573ccbd19b782e4f6e5930a8f944517884fe02d26eb0f38bf5c3ac  Mk3ChangeLog.md
 a0c4d0ac3881a36704f0b620a13c72704531f656ee29368d5aac87dc5f21c7a1  History.md
-b4255a8ed247ed8cc32c3b25d6380d6202bdb86357e5d6864abaac144ff95692  ChangeLog.md
+9f91f9dba7dfd7663586e132181ffc6e2752da1c2ba146f15ba45c1eaa2420c0  ChangeLog.md
+8b82811a7729eeaa0d9dd45fab4b74b37706a9fd6d045e6b06070a935d774613  2023-12-18T1636-v5.2.1-mk4-coldcard.dfu
+d9bbb2ceeeec8c4279491f614a403001c3be1a5804bdd8ecd88d9fb2c2c9f50a  2023-12-18T1636-v5.2.1-mk4-coldcard-factory.dfu
 f4457dc44d08cbed9517e6260aa7163ecc254457276d3cdb0c2611af0f49ba9b  2023-10-26T1343-v6.2.1X-mk4-coldcard.dfu
 1dcfb450f81883afe8f655239f06e238de7bae51e740cd4aa5ae6a0541772ad8  2023-10-26T1343-v6.2.1X-mk4-coldcard-factory.dfu
 7fbed097d2757b21fde920f4b10f5f50d7e1aeca01ff52186dfde4883af5cace  2023-10-10T1735-v5.2.0-mk4-coldcard.dfu
@@ -47,12 +49,12 @@ f05bc8dfed047c0c0abe5ed60621d2d14899b10717221c4af0942d96a1754f33  2021-03-29T192
 bea27f263b524a66b3ed0a58c16805e98be0d7c3db20c2f7aab3238f2c6a6995  2019-12-19T1623-v3.0.6-coldcard.dfu
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diff --git a/stm32/COLDCARD_MK4/file_time.c b/stm32/COLDCARD_MK4/file_time.c
index a5e81cd0..c7ba501c 100644
--- a/stm32/COLDCARD_MK4/file_time.c
+++ b/stm32/COLDCARD_MK4/file_time.c
@@ -2,12 +2,12 @@
 //
 // AUTO-generated.
 //
-//   built: 2023-10-10
-// version: 5.2.0
+//   built: 2023-12-18
+// version: 5.2.1
 //
 #include <stdint.h>
 
 // this overrides ports/stm32/fatfs_port.c
 uint32_t get_fattime(void) {
-    return 0x574a2840UL;
+    return 0x57922840UL;
 }