diff --git a/code/robots.py b/code/robots.py
index e63d2bd..8b72388 100755
--- a/code/robots.py
+++ b/code/robots.py
@@ -178,27 +178,27 @@ def list_to_pcre(robots_json):
     patterns = []
 
     # regular old substring matches:
-    formatted = "|".join(
+    formatted = "|".join([
         f"{re.escape(agent)}"
         for agent, config in robots_json.items()
         if not config.get("sends_full_name", False) and not config.get("has_name_and_version", False)
-    )
+    ])
     patterns.extend( f"({formatted})" )
 
     # agents that just send their names pokemon-style
-    exact_agents = "|".join(
+    exact_agents = "|".join([
         f"^{re.escape(agent)}$"
         for agent, config in robots_json.items()
         if config.get("sends_full_name", False)
-    )
+    ])
     patterns.extend( f"^({exact_agents})$" )
 
     # agents who use Name/1.1.3-style elements 
-    versioned_agents = "|".join(
+    versioned_agents = "|".join([
         f"{re.escape(agent)}/[0-9.]+"
         for agent, config in robots_json.items()
         if config.get("has_name_and_version", False)
-    )
+    ])
     patterns.extend( versioned_agents )
         
     return f"({'|'.join(patterns)})"