diff --git a/photoapp/daemon.py b/photoapp/daemon.py
index fb163d4..5106a8f 100644
--- a/photoapp/daemon.py
+++ b/photoapp/daemon.py
@@ -7,21 +7,19 @@ from collections import defaultdict
 from urllib.parse import urlparse
 from datetime import datetime, timedelta
 from photoapp.thumbtool import ThumbGenerator
-from photoapp.types import Photo, PhotoSet, Tag, TagItem, PhotoStatus, User, mime2ext, regular_mimes, video_mimes
+from photoapp.types import APPROOT, Photo, PhotoSet, Tag, TagItem, PhotoStatus, User, mime2ext, \
+    regular_mimes, video_mimes
 from photoapp.dbsession import DatabaseSession
 from photoapp.common import pwhash
 from photoapp.api import PhotosApi, LibraryManager
 from photoapp.dbutils import SAEnginePlugin, SATool, db, get_db_engine, date_format
 from photoapp.utils import auth, require_auth, photoset_auth_filter, slugify, cherryparam, number_format
 from photoapp.storage import uri_to_storage
-from photoapp.webutils import validate_password
+from photoapp.webutils import validate_password, serve_thumbnail_placeholder
 from jinja2 import Environment, FileSystemLoader, select_autoescape
 from sqlalchemy import desc, func, and_, or_
 
 
-APPROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "../"))
-
-
 class PhotosWeb(object):
     """
     Http root of the UI webserver
@@ -272,14 +270,15 @@ class ThumbnailView(object):
             t = vtypes.pop()  # TODO arbitrary
             thumb_from = formats[t][0]  # TODO arbitrary
 
+        if not thumb_from:  # no format we know how to make a thumbnail from was found
+            return serve_thumbnail_placeholder()
+
         thumb_fobj = self.master.thumbtool.make_thumb(thumb_from, thumb_size)
 
         if thumb_fobj:
             return cherrypy.lib.static.serve_fileobj(thumb_fobj, "image/jpeg")
-        else:
-            cherrypy.response.headers["Cache-Control"] = "no-store, must-revalidate, max-age=0"
-            cherrypy.response.headers["Age"] = "0"
-            return cherrypy.lib.static.serve_file(os.path.join(APPROOT, "assets/img/unknown.svg"), "image/svg+xml")
+        else:   # thumb creation failed or in progress
+            return serve_thumbnail_placeholder(True)
 
 
 @cherrypy.popargs('item_type', 'uuid')
diff --git a/photoapp/types.py b/photoapp/types.py
index 72e4faf..b2c8aa7 100644
--- a/photoapp/types.py
+++ b/photoapp/types.py
@@ -3,11 +3,15 @@ from sqlalchemy.orm import relationship
 from sqlalchemy.schema import UniqueConstraint
 from photoapp.dbutils import Base
 from datetime import datetime
+import os
 import enum as py_enum
 import uuid
 import enum
 
 
+APPROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "../"))
+
+
 class fcategory(py_enum.Enum):
     image = 0
     raw = 1
diff --git a/photoapp/webutils.py b/photoapp/webutils.py
index 87426eb..a862a16 100644
--- a/photoapp/webutils.py
+++ b/photoapp/webutils.py
@@ -1,4 +1,6 @@
-from photoapp.types import User
+import os
+import cherrypy
+from photoapp.types import APPROOT, User
 from photoapp.dbutils import db
 from photoapp.common import pwhash
 
@@ -7,3 +9,13 @@ def validate_password(realm, username, password):
     if db.query(User).filter(User.name == username, User.password == pwhash(password)).first():
         return True
     return False
+
+
+def serve_thumbnail_placeholder(temporary=False):
+    """
+    Serve the placeholder for broken/unavailable thumbnails, the <?> image. Setting temporary will add a no-cache header
+    """
+    if temporary:
+        cherrypy.response.headers["Cache-Control"] = "no-store, must-revalidate, max-age=0"
+        cherrypy.response.headers["Age"] = "0"
+    return cherrypy.lib.static.serve_file(os.path.join(APPROOT, "assets/img/unknown.svg"), "image/svg+xml")