diff --git a/services/radio/RadioService.h b/services/radio/RadioService.h
index 49feda6..ac3481e 100644
--- a/services/radio/RadioService.h
+++ b/services/radio/RadioService.h
@@ -103,7 +103,7 @@
     class CallbackThread : public Thread {
     public:
 
-        CallbackThread(const wp<ModuleClient>& moduleClient);
+        explicit CallbackThread(const wp<ModuleClient>& moduleClient);
 
         virtual ~CallbackThread();