diff --git a/src/octoprint/server/__init__.py b/src/octoprint/server/__init__.py
index 92df48c9..b1977085 100644
--- a/src/octoprint/server/__init__.py
+++ b/src/octoprint/server/__init__.py
@@ -943,12 +943,7 @@ class Server():
 			"css/pnotify.min.css"
 		]
 		css_app = list(dynamic_assets["css"])
-		if len(css_app) == 0:
-			css_app = ["empty"]
-
 		less_app = list(dynamic_assets["less"])
-		if len(less_app) == 0:
-			less_app = ["empty"]
 
 		from webassets.filter import register_filter, Filter
 		from webassets.filter.cssrewrite.base import PatternRewriter
@@ -988,9 +983,16 @@ class Server():
 			js_app_bundle = Bundle(*js_app, output="webassets/packed_app.js", filters="js_delimiter_bundler")
 
 		css_libs_bundle = Bundle(*css_libs, output="webassets/packed_libs.css")
-		css_app_bundle = Bundle(*css_app, output="webassets/packed_app.css", filters="cssrewrite")
 
-		all_less_bundle = Bundle(*less_app, output="webassets/packed_app.less", filters="cssrewrite, less_importrewrite")
+		if len(css_app) == 0:
+			css_app_bundle = Bundle(*[])
+		else:
+			css_app_bundle = Bundle(*css_app, output="webassets/packed_app.css", filters="cssrewrite")
+
+		if len(less_app) == 0:
+			all_less_bundle = Bundle(*[])
+		else:
+			all_less_bundle = Bundle(*less_app, output="webassets/packed_app.less", filters="cssrewrite, less_importrewrite")
 
 		assets.register("js_libs", js_libs_bundle)
 		assets.register("js_client", js_client_bundle)
@@ -1126,4 +1128,3 @@ class LifecycleManager(object):
 			for event in events:
 				if callback in self._plugin_lifecycle_callbacks[event]:
 					self._plugin_lifecycle_callbacks[event].remove(callback)
-