diff --git a/timesearch/commentaugment.py b/timesearch/commentaugment.py
index 26a33bf..9c9b09e 100644
--- a/timesearch/commentaugment.py
+++ b/timesearch/commentaugment.py
@@ -20,10 +20,9 @@ def commentaugment(
         raise exceptions.NotExclusive(['username', 'specific_submission'])
 
     common.login()
+
     if specific_submission is not None:
-        specific_submission = common.t3_prefix(specific_submission)[3:]
-        specific_submission_obj = common.r.submission(specific_submission)
-        subreddit = specific_submission_obj.subreddit.display_name
+        subreddit = common.subreddit_for_submission(specific_submission).display_name
 
     if subreddit:
         do_create = specific_submission is not None
diff --git a/timesearch/common.py b/timesearch/common.py
index 81b1872..df5a458 100644
--- a/timesearch/common.py
+++ b/timesearch/common.py
@@ -127,6 +127,11 @@ def split_any(text, delimiters):
         text = text.replace(replacer, splitter)
     return text.split(splitter)
 
+def subreddit_for_submission(submission_id):
+    submission_id = t3_prefix(submission_id)[3:]
+    submission = r.submission(submission_id)
+    return submission.subreddit
+
 def t3_prefix(submission_id):
     if not submission_id.startswith('t3_'):
         submission_id = 't3_' + submission_id
diff --git a/timesearch/offline_reading.py b/timesearch/offline_reading.py
index d1d91a2..a794d78 100644
--- a/timesearch/offline_reading.py
+++ b/timesearch/offline_reading.py
@@ -222,8 +222,13 @@ def html_from_database(subreddit=None, username=None, specific_submission=None):
     if markdown is None:
         raise ImportError('Page cannot be rendered without the markdown module')
 
-    if not common.is_xor(subreddit, username):
+    if not specific_submission and not common.is_xor(subreddit, username):
         raise exceptions.NotExclusive(['subreddit', 'username'])
+    if username and specific_submission:
+        raise exceptions.NotExclusive(['username', 'specific_submission'])
+
+    if specific_submission is not None:
+        subreddit = common.subreddit_for_submission(specific_submission).display_name
 
     if subreddit:
         database = tsdb.TSDB.for_subreddit(subreddit, do_create=False)