diff --git a/offlineimap.conf b/offlineimap.conf
index ff788f9..61191b9 100644
--- a/offlineimap.conf
+++ b/offlineimap.conf
@@ -787,8 +787,11 @@ remotehost = examplehost
 #
 # In Windows, Microsoft uses the term "thumbprint" instead of "fingerprint".
 #
-# Fingerprints must be in hexadecimal form without leading '0x':
-# 40 hex digits like bbfe29cf97acb204591edbafe0aa8c8f914287c9.
+# Fingerprints must be in hexadecimal form without leading '0x', and may have
+# the separating colons. This is non case-sensitive.
+# Examples:
+# sha1 "bbfe29cf97acb204591edbafe0aa8c8f914287c9".
+# sha1 with colons "BB:FE:29:CF:97:AC:B2:04:59:1E:DB:AF:E0:AA:8C:8F:91:42:87:C9"
 #
 #cert_fingerprint = <SHA1_of_server_certificate_here>[, <another_SHA1>]