diff --git a/ptulsconv/broadcast_timecode.py b/ptulsconv/broadcast_timecode.py
index d771767..4c8af71 100644
--- a/ptulsconv/broadcast_timecode.py
+++ b/ptulsconv/broadcast_timecode.py
@@ -2,7 +2,7 @@ from fractions import Fraction
 import re
 import math
 from collections import namedtuple
-from typing import Optional
+from typing import Optional, SupportsFloat
 
 class TimecodeFormat(namedtuple("_TimecodeFormat", "frame_duration logical_fps drop_frame")):
 
@@ -13,7 +13,7 @@ class TimecodeFormat(namedtuple("_TimecodeFormat", "frame_duration logical_fps d
         else:
             return frame_count * self.frame_duration
 
-    def seconds_to_smpte(self, seconds: Fraction) -> str:
+    def seconds_to_smpte(self, seconds: SupportsFloat) -> str:
         frame_count = int(seconds / self.frame_duration)
         return frame_count_to_smpte(frame_count, self.logical_fps, self.drop_frame)
 
diff --git a/ptulsconv/commands.py b/ptulsconv/commands.py
index cc80979..3493bc0 100644
--- a/ptulsconv/commands.py
+++ b/ptulsconv/commands.py
@@ -5,6 +5,7 @@ import sys
 from itertools import chain
 import csv
 from typing import List
+from fractions import Fraction
 
 from .docparser.adr_entity import make_entities
 from .reporting import print_section_header_style, print_status_style, print_warning
@@ -59,10 +60,12 @@ def output_adr_csv(lines: List[ADRLine], time_format: TimecodeFormat):
                                  'Reason', 'Note', 'TV'])
 
                 for event in these_lines:
+                    this_start = event.start or 0
+                    this_finish = event.finish or 0
                     this_row = [event.title, event.character_name, event.cue_number,
                                 event.reel, event.version,
-                                time_format.seconds_to_smpte(event.start), time_format.seconds_to_smpte(event.finish),
-                                float(event.start), float(event.finish),
+                                time_format.seconds_to_smpte(this_start), time_format.seconds_to_smpte(this_finish),
+                                float(this_start), float(this_finish),
                                 event.prompt,
                                 event.reason, event.note, "TV" if event.tv else ""]