diff --git a/components/bt/common/ble_log/include/ble_log.h b/components/bt/common/ble_log/include/ble_log.h
index 0a358a34f34..7668faf4d48 100644
--- a/components/bt/common/ble_log/include/ble_log.h
+++ b/components/bt/common/ble_log/include/ble_log.h
@@ -45,14 +45,17 @@ typedef enum {
 #define BLE_LOG_HCI_DOWNSTREAM  0
 #define BLE_LOG_HCI_UPSTREAM    1
 
-/* HCI Log Write Macro
- * Encodes direction in MSB of data[0] (HCI type byte) before writing.
- * Safe because ble_log_write_hex -> ble_log_lbm_write_trans does synchronous memcpy.
- * Parser reads MSB to determine direction; old firmware with MSB=0 defaults to "sent". */
-#define ble_log_write_hci(direction, data, len) do {    \
-    (data)[0] |= ((direction) << 7);                   \
-    ble_log_write_hex(BLE_LOG_SRC_HCI, (data), (len)); \
-    (data)[0] &= 0x7F;                                 \
+/* Encodes HCI direction in payload byte 0 bit 7 for the synchronous copy,
+ * then restores the complete original HCI type byte. The caller guarantees a
+ * non-NULL buffer with len > 0. */
+#define ble_log_write_hci(direction, data, len) do {                  \
+    uint8_t *const ble_log_hci_data__ = (data);                       \
+    const uint8_t ble_log_hci_type__ = ble_log_hci_data__[0];         \
+    ble_log_hci_data__[0] = (ble_log_hci_type__ & 0x7fU) |            \
+                            ((direction) ? 0x80U : 0U);               \
+    (void)ble_log_write_hex(BLE_LOG_SRC_HCI, ble_log_hci_data__,      \
+                            (len));                                   \
+    ble_log_hci_data__[0] = ble_log_hci_type__;                       \
 } while (0)
 
 /* INTERFACE */