diff --git a/Makefile b/Makefile
index 2501cf3b7..47004bae5 100644
--- a/Makefile
+++ b/Makefile
@@ -1078,6 +1078,7 @@ clean:
 	$(Q)rm -f addons/promex/*.[oas]
 	$(Q)rm -f addons/51degrees/*.[oas] addons/51degrees/dummy/*.[oas] addons/51degrees/dummy/*/*.[oas]
 	$(Q)rm -f addons/deviceatlas/*.[oas] addons/deviceatlas/dummy/*.[oas] addons/deviceatlas/dummy/*.o
+	$(Q)rm -f addons/deviceatlas/dummy/Os/*.o
 	$(Q)rm -f addons/ot/src/*.[oas]
 	$(Q)rm -f addons/wurfl/*.[oas] addons/wurfl/dummy/*.[oas]
 	$(Q)rm -f admin/*/*.[oas] admin/*/*/*.[oas]