diff --git a/dlibrary/dlibrary.py b/dlibrary/dlibrary.py
index 3d49ca0..acc71b0 100755
--- a/dlibrary/dlibrary.py
+++ b/dlibrary/dlibrary.py
@@ -20,6 +20,8 @@ import requests
 
 NUMBER_REGEX = re.compile('[0-9]+')
 
+DLSITE_ID_REGEX = re.compile('^[BR]J[0-9]+$')
+
 IMAGE_FILE_EXTENSIONS = ['.png', '.jpg', '.jpeg', '.gif', '.tiff']
 
 IGNOREABLE_FILES = ['Thumbs.db', '__MACOSX', '.DS_Store']
@@ -69,6 +71,10 @@ async def fetch_async(args):
             if res.fetchone() is not None:
                 continue
 
+            if not DLSITE_ID_REGEX.fullmatch(work_id):
+                print(f"{work_id} doesn't seem to be from DLSite, not attempting to fetch metadata")
+                continue
+
             print(f'Fetching metadata for {work_id}')
             metadata = await api.get_work(work_id)