diff --git a/utils/service_discovery/sd_docker_backend.py b/utils/service_discovery/sd_docker_backend.py
index 02b2f946aa..608e14fcf5 100644
--- a/utils/service_discovery/sd_docker_backend.py
+++ b/utils/service_discovery/sd_docker_backend.py
@@ -494,7 +494,10 @@ def _fill_tpl(self, state, c_id, instance_tpl, variables, c_tags=None):
         c_image = state.inspect_container(c_id).get('Config', {}).get('Image', '')
 
         # add only default c_tags to the instance to avoid duplicate tags from conf
-        tags = c_tags[:]
+        if c_tags:
+            tags = c_tags[:] # shallow copy of the c_tags array
+        else
+            tags = []
         if tags:
             tpl_tags = instance_tpl.get('tags', [])
             if isinstance(tpl_tags, dict):