diff --git a/adafruit_gps.py b/adafruit_gps.py
index 2aca02a..7cb4468 100644
--- a/adafruit_gps.py
+++ b/adafruit_gps.py
@@ -248,6 +248,8 @@ def update(self):
         if self.debug:
             print(sentence)
         data_type, args = sentence
+        if len(data_type) < 5:
+            return False
         data_type = bytes(data_type.upper(), "ascii")
         (talker, sentence_type) = _parse_talker(data_type)