diff --git a/bundles/org.openhab.core.transform/src/main/java/org/eclipse/smarthome/core/transform/AbstractFileTransformationService.java b/bundles/org.openhab.core.transform/src/main/java/org/eclipse/smarthome/core/transform/AbstractFileTransformationService.java
index 64e7f165b..e0ca6eb0f 100644
--- a/bundles/org.openhab.core.transform/src/main/java/org/eclipse/smarthome/core/transform/AbstractFileTransformationService.java
+++ b/bundles/org.openhab.core.transform/src/main/java/org/eclipse/smarthome/core/transform/AbstractFileTransformationService.java
@@ -57,6 +57,7 @@ public abstract class AbstractFileTransformationService<T> implements Transforma
     private @Nullable WatchService watchService = null;
 
     protected final Map<String, T> cachedFiles = new ConcurrentHashMap<>();
+    private final Map<WatchKey, Path> registeredKeys = new ConcurrentHashMap<>();
     protected final List<String> watchedDirectories = new ArrayList<String>();
 
     private final Logger logger = LoggerFactory.getLogger(AbstractFileTransformationService.class);
@@ -98,6 +99,7 @@ public abstract class AbstractFileTransformationService<T> implements Transforma
 
     protected void deactivate() {
         localeProviderTracker.close();
+        stopWatchService();
     }
 
     protected Locale getLocale() {
@@ -187,9 +189,10 @@ public abstract class AbstractFileTransformationService<T> implements Transforma
             String watchedDirectory = getSourcePath() + subDirectory;
             Path transformFilePath = Paths.get(watchedDirectory);
             try {
-                transformFilePath.register(watchService, ENTRY_DELETE, ENTRY_MODIFY);
+                WatchKey registrationKey = transformFilePath.register(watchService, ENTRY_DELETE, ENTRY_MODIFY);
                 logger.debug("Watching directory {}", transformFilePath);
                 watchedDirectories.add(subDirectory);
+                registeredKeys.put(registrationKey, transformFilePath);
             } catch (IOException e) {
                 logger.warn("Unable to watch transformation directory : {}", watchedDirectory);
                 cachedFiles.clear();
@@ -225,6 +228,23 @@ public abstract class AbstractFileTransformationService<T> implements Transforma
         }
     }
 
+    private synchronized void stopWatchService() {
+        if (watchService != null) {
+            for (WatchKey watchKey : registeredKeys.keySet()) {
+                watchKey.cancel();
+            }
+            registeredKeys.clear();
+            watchedDirectories.clear();
+            try {
+                watchService.close();
+            } catch (IOException e) {
+                logger.warn("Cannot deactivate transformation directory watcher", e);
+            }
+            watchService = null;
+            cachedFiles.clear();
+        }
+    }
+
     /**
      * Returns the name of the localized transformation file
      * if it actually exists, keeps the original in the other case