diff --git a/fdbclient/MasterProxyInterface.h b/fdbclient/MasterProxyInterface.h
index 8775115264..cf3561bbd5 100644
--- a/fdbclient/MasterProxyInterface.h
+++ b/fdbclient/MasterProxyInterface.h
@@ -239,7 +239,7 @@ struct GetHealthMetricsRequest
 	ReplyPromise<struct GetHealthMetricsReply> reply;
 	bool detailed;
 
-	GetHealthMetricsRequest(bool detailed = false) : detailed(detailed) {}
+	explicit GetHealthMetricsRequest(bool detailed = false) : detailed(detailed) {}
 
 	template <class Ar>
 	void serialize(Ar& ar)