diff --git a/bookwyrm/settings.py b/bookwyrm/settings.py
index 0fe21232..4d38e082 100644
--- a/bookwyrm/settings.py
+++ b/bookwyrm/settings.py
@@ -191,7 +191,7 @@ USER_AGENT = f"{agent} (BookWyrm/{VERSION}; +https://{DOMAIN}/)"
 ENABLE_THUMBNAIL_GENERATION = env.bool("ENABLE_THUMBNAIL_GENERATION", False)
 IMAGEKIT_CACHEFILE_DIR = "thumbnails"
 #IMAGEKIT_DEFAULT_CACHEFILE_BACKEND = "imagekit.cachefiles.backends.Celery"
-IMAGEKIT_DEFAULT_CACHEFILE_STRATEGY = "imagekit.cachefiles.strategies.Optimistic"
+IMAGEKIT_DEFAULT_CACHEFILE_STRATEGY = "bookwyrm.thumbnail_generation.Strategy"
 
 # Static files (CSS, JavaScript, Images)
 # https://docs.djangoproject.com/en/3.2/howto/static-files/
diff --git a/bookwyrm/thumbnail_generation.py b/bookwyrm/thumbnail_generation.py
new file mode 100644
index 00000000..fb9b9c38
--- /dev/null
+++ b/bookwyrm/thumbnail_generation.py
@@ -0,0 +1,14 @@
+class Strategy:
+    """
+    A strategy that generates the image on source saved (Optimistic),
+    but also on demand, for old images (JustInTime).
+    """
+
+    def on_source_saved(self, file):
+        file.generate()
+
+    def on_existence_required(self, file):
+        file.generate()
+
+    def on_content_required(self, file):
+        file.generate()