diff --git a/webvtt/structures.py b/webvtt/structures.py
index 84f376d..c4a576d 100644
--- a/webvtt/structures.py
+++ b/webvtt/structures.py
@@ -2,7 +2,7 @@
 
 from .errors import MalformedCaptionError
 
-TIMESTAMP_PATTERN = re.compile('(\d+)?:?(\d{2}):(\d{2})[.,](\d{3})')
+TIMESTAMP_PATTERN = re.compile(r'(\d+)?:?(\d{2}):(\d{2})[.,](\d{3})')
 
 __all__ = ['Caption']