diff --git a/bk7231tools/serial/cmd_chip.py b/bk7231tools/serial/cmd_chip.py
index 6b3ec55..32a6f3a 100644
--- a/bk7231tools/serial/cmd_chip.py
+++ b/bk7231tools/serial/cmd_chip.py
@@ -72,6 +72,9 @@ def read_chip_info(self) -> str:
             self.chip_info, _ = CHIP_BY_CRC[crc]
             # read the protocol here already - it might not support BootVersion
             self.protocol_type = PROTOCOLS.get(self.chip_info, ProtocolType.UNKNOWN)
+        else:
+            # unknown bootloader version - assume minimal protocol support
+            self.protocol_type = ProtocolType.BASIC_DEFAULT
 
         # try BK7231S chip info command
         command = BkBootVersionCmnd()
@@ -89,7 +92,7 @@ def read_chip_info(self) -> str:
             default = ProtocolType.FULL
         else:
             self.chip_info = response.version.decode().strip("\x00\x20")
-            default = ProtocolType.BASIC_DEFAULT
+            default = ProtocolType.BASIC_TUYA
 
         # get protocol by chip info or SCTRL_CHIP_ID
         # if not set, use `default`
diff --git a/bk7231tools/serial/protocol.py b/bk7231tools/serial/protocol.py
index e647a65..ee6cd45 100644
--- a/bk7231tools/serial/protocol.py
+++ b/bk7231tools/serial/protocol.py
@@ -60,7 +60,7 @@ class ProtocolType(Enum):
         (0x09, LONG),  # CMD_FlashRead4K
         (0x0F, LONG),  # CMD_FlashErase
     ]
-    BASIC_DEFAULT = BASIC_TUYA
+    BASIC_DEFAULT = BASIC_BEKEN
 
 
 # list of protocols with verified command support