diff --git a/libretroshare/src/util/rsthreads.h b/libretroshare/src/util/rsthreads.h
index d1ed91dc9..edec70472 100644
--- a/libretroshare/src/util/rsthreads.h
+++ b/libretroshare/src/util/rsthreads.h
@@ -105,7 +105,7 @@ class RsStackMutex
 {
 public:
 
-	RsStackMutex(RsMutex &mtx) : mMtx(mtx)
+	explicit RsStackMutex(RsMutex& mtx): mMtx(mtx)
 	{
 		mMtx.lock();
 #ifdef RS_MUTEX_DEBUG