diff --git a/tools/nasparse.py b/tools/nasparse.py
index 61713b1..c78ed3b 100755
--- a/tools/nasparse.py
+++ b/tools/nasparse.py
@@ -26,7 +26,7 @@ def parse_nas_message(buffer, uplink=None):
         parsed = NASLTE.parse_NASLTE_MT(bin)
     
     if parsed[0] is None: # Not a NAS Packet 
-        raise parsed[1]
+        raise TypeError("Not a nas packet")
     return parsed[0]
 
 def heur_ue_imsi_sent(msg):
diff --git a/tools/nasparse_test.py b/tools/nasparse_test.py
index c877e0b..bba24be 100644
--- a/tools/nasparse_test.py
+++ b/tools/nasparse_test.py
@@ -6,7 +6,7 @@ import nasparse
 class TestNasparse(unittest.TestCase):
     imsi_sent_msg = '07412208391185184409309005f0700000100030023ed031d127298080211001000010810600000000830600000000000d00000300ff0003130184000a000005000010005c0a009011034f18a6f15d0103c1000000000000'
     sec_imsi_sent_msg = '1727db4b7c0207412208391185184409309005f0700000100030023ed031d127298080211001000010810600000000830600000000000d00000300ff0003130184000a000005000010005c0a009011034f18a6f15d0103c1'
-    non_nas_msg = '1312deadbeefcafe'
+    non_nas_msg = 'deadbeefcafe'
     other_nas_msg = '074413780004023fd121'
     other_nas_mt_msg = "023fd12100000000000000000000000000000000000000000000000000000000"
     ciphered_nas_msg = "27ed6146bd0162a5d62d62e1ce501720dc8bd84f1167fd"
@@ -22,7 +22,8 @@ class TestNasparse(unittest.TestCase):
         self.assertEqual(self.run_heur(self.imsi_sent_msg), True, "sec_imsi_sent_msg should trigger heuristic")
 
     def test_non_nas_msg(self):
-        self.assertEqual(self.run_heur(self.non_nas_msg), False, "non_nas_msg should not trigger heuristic")
+        with self.assertRaises(TypeError):
+            self.run_heur(self.non_nas_msg)
 
     def test_other_nas(self):
         self.assertEqual(self.run_heur(self.other_nas_msg), False, "other_nas_msg should not trigger heuristic")