diff --git a/src/main/java/net/openhft/chronicle/map/FilePerKeyMap.java b/src/main/java/net/openhft/chronicle/map/FilePerKeyMap.java
index 758c6b291..0798e83de 100644
--- a/src/main/java/net/openhft/chronicle/map/FilePerKeyMap.java
+++ b/src/main/java/net/openhft/chronicle/map/FilePerKeyMap.java
@@ -58,6 +58,7 @@ public class FilePerKeyMap implements Map<String, String>, Closeable {
         );
 
         fileFpmWatcher = new Thread(new FPMWatcher(watcher), dir + "-watcher");
+        fileFpmWatcher.setDaemon(true);
         fileFpmWatcher.start();
     }