diff --git a/API.md b/API.md
index df834154..27d4de71 100644
--- a/API.md
+++ b/API.md
@@ -169,6 +169,7 @@ List of possible error names:
 - `InvalidPasswordError`
 - `InvalidRankError`
 - `InvalidAvatarError`
+- `ProcessingError` (failed to generate thumbnail or download remote file)
 - `ValidationError` (catch all for odd validation errors)
 
 
diff --git a/server/szurubooru/func/net.py b/server/szurubooru/func/net.py
index 65c01c00..62ac4c37 100644
--- a/server/szurubooru/func/net.py
+++ b/server/szurubooru/func/net.py
@@ -1,9 +1,13 @@
 import urllib.request
+from szurubooru import errors
 
 
 def download(url):
     assert url
     request = urllib.request.Request(url)
     request.add_header('Referer', url)
-    with urllib.request.urlopen(request) as handle:
-        return handle.read()
+    try:
+        with urllib.request.urlopen(request) as handle:
+            return handle.read()
+    except Exception as e:
+        raise errors.ProcessingError('Error downloading %s (%s)' % (url, e))