diff --git a/bmspy/jbd_bms.py b/bmspy/jbd_bms.py
index 455d497..bcf3732 100644
--- a/bmspy/jbd_bms.py
+++ b/bmspy/jbd_bms.py
@@ -116,7 +116,8 @@ def collect_data(ser: serial.Serial, debug: int = 0) -> JBDBMS | bool:
     reqmsg = bytearray([0xDD, 0xA5, 0x03, 0x00, 0xFF, 0xFD, 0x77])
     response_03 = requestMessage(ser, reqmsg, debug)
 
-    if len(response_03) == 0:
+    # A port that cannot open returns False or None, not an empty response.
+    if not response_03:
         if debug > 0:
             debugger("collect_data: Error retrieving BMS info. Trying again...")
         return False
@@ -125,7 +126,7 @@ def collect_data(ser: serial.Serial, debug: int = 0) -> JBDBMS | bool:
     reqmsg = bytearray([0xDD, 0xA5, 0x04, 0x00, 0xFF, 0xFC, 0x77])
     response_04 = requestMessage(ser, reqmsg, debug)
 
-    if len(response_04) == 0:
+    if not response_04:
         if debug > 0:
             debugger("collect_data: Error retrieving BMS info. Trying again...")
         return False