diff --git a/src/xpra/server/mixins/webcam_server.py b/src/xpra/server/mixins/webcam_server.py
index 33748f1590..a494a8f93b 100644
--- a/src/xpra/server/mixins/webcam_server.py
+++ b/src/xpra/server/mixins/webcam_server.py
@@ -26,6 +26,7 @@ def __init__(self):
         self.webcam_device = ""
         self.webcam_encodings = []
         self.webcam_enabled = False
+        self.webcam_virtual_video_devices = 0
 
     def init(self, opts):
         self.webcam_enabled = opts.webcam.lower() not in FALSE_OPTIONS