diff --git a/src/cached_traffic_control.rs b/src/cached_traffic_control.rs
index 32c1d0c8..df2ba2f8 100644
--- a/src/cached_traffic_control.rs
+++ b/src/cached_traffic_control.rs
@@ -348,6 +348,7 @@ rule: somewhere
 
         let mut cache = TrafficControlCache::new();
         cache.use_utc = true;
+        cache.use_shared_memory = false; // avoid permission problems in test environment
 
         cache.update_config(&config)?;