diff --git a/lib/nntp/tiny/session.py b/lib/nntp/tiny/session.py
index 537c50c..5cd6b6c 100644
--- a/lib/nntp/tiny/session.py
+++ b/lib/nntp/tiny/session.py
@@ -21,10 +21,10 @@ class SessionState(enum.Flag):
 class MessageRange():
     __slots__ = 'id', 'min', 'max',
 
-    RE_NUM         = re.compile('^(\d+)$')
-    RE_RANGE       = re.compile('^(\d+)-(\d+)$')
-    RE_RANGE_LOWER = re.compile('^(\d+$)-$')
-    RE_RANGE_UPPER = re.compile('^-(\d+$)$')
+    RE_NUM         = re.compile(r'^(\d+)$')
+    RE_RANGE       = re.compile(r'^(\d+)-(\d+)$')
+    RE_RANGE_LOWER = re.compile(r'^(\d+$)-$')
+    RE_RANGE_UPPER = re.compile(r'^-(\d+$)$')
 
     def __init__(self):
         self.id:  int = None