diff --git a/storage/backup.c b/storage/backup.c
index 2842eb7..9ab3de7 100644
--- a/storage/backup.c
+++ b/storage/backup.c
@@ -36,9 +36,15 @@ static backup_key_t to_backup_key(const key_record_t *k) {
 
 static key_record_t to_key_record(const backup_key_t *b) {
     key_record_t k;
-    k.id                = b->id;
-    k.is_enabled        = b->is_enabled;
-    k.is_admin          = b->is_admin;
+    k.id = b->id;
+    // The backup blob is untrusted input: its is_enabled/is_admin bytes may hold
+    // any value, so read them as raw bytes and canonicalise. Loading a `bool`
+    // whose object representation is not 0/1 is undefined behaviour.
+    uint8_t enabled_raw, admin_raw;
+    memcpy(&enabled_raw, &b->is_enabled, sizeof(enabled_raw));
+    memcpy(&admin_raw, &b->is_admin, sizeof(admin_raw));
+    k.is_enabled        = (enabled_raw != 0);
+    k.is_admin          = (admin_raw != 0);
     k.created_at        = b->created_at;
     k.is_checksum_valid = true;
     memcpy(k.name, b->name, sizeof(k.name));
diff --git a/test/harness_storage.c b/test/harness_storage.c
index fd929f3..a74bd60 100644
--- a/test/harness_storage.c
+++ b/test/harness_storage.c
@@ -28,6 +28,7 @@
 #include "pico/stdlib.h"    /* PICO_FLASH_SIZE_BYTES, PICO_OK */
 
 #include "backup.h"
+#include "lfs_util.h" /* lfs_crc: matches backup.c's whole-backup checksum */
 #include "storage.h"
 
 /* Must match storage.c's private layout constants. */
@@ -250,6 +251,34 @@ int main(void) {
     assert(backup_import(backup, (size_t)elen) == true);
     assert(storage_key_list(list, 16) == 0);
 
+    /* --- UBSan regression: non-bool flag byte in an otherwise-valid blob --- */
+    /* to_key_record() must not load is_enabled/is_admin straight into a `bool`:
+     * a crafted import blob can carry any byte there, and loading a bool whose
+     * object representation is not 0/1 is undefined behaviour (caught by
+     * -fsanitize=undefined). Build a valid 1-key blob, poke a non-bool flag
+     * byte, refresh the header CRC so the blob still validates, and import it.
+     * The import must succeed and the flag must read back canonicalised. */
+    {
+        key_record_t seed = make_key(9, "ub", true, false, 1234, 0x40);
+        assert(storage_key_save(&seed) == true);
+        uint8_t craft[sizeof backup];
+        int     clen = backup_export(craft, sizeof craft);
+        assert((size_t)clen == sizeof(backup_header_t) + sizeof(backup_key_t));
+        assert(storage_key_delete(9) == true);
+
+        backup_key_t *bk          = (backup_key_t *)(craft + sizeof(backup_header_t));
+        *(uint8_t *)&bk->is_admin = 67; /* non-bool byte in an otherwise-valid record */
+        backup_header_t *bh       = (backup_header_t *)craft;
+        bh->checksum              = lfs_crc(0xFFFFFFFF, bk, sizeof(backup_key_t));
+
+        assert(backup_import(craft, (size_t)clen) == true);
+        key_record_t g;
+        assert(storage_key_get(9, &g) == true);
+        assert(g.is_admin == true);   /* canonicalised: exactly 1, not 67 */
+        assert(g.is_enabled == true); /* untouched flag survives */
+        assert(storage_key_delete(9) == true);
+    }
+
     printf("storage OK\n");
     return 0;
 }