diff --git a/userspace/engine/indexable_ruleset.h b/userspace/engine/indexable_ruleset.h
index 4da90e07..f02d3938 100644
--- a/userspace/engine/indexable_ruleset.h
+++ b/userspace/engine/indexable_ruleset.h
@@ -229,7 +229,7 @@ private:
 	// A group of filters all having the same ruleset
 	class ruleset_filters {
 	public:
-		ruleset_filters(uint16_t ruleset_id): m_ruleset_id(ruleset_id) {}
+		explicit ruleset_filters(uint16_t ruleset_id): m_ruleset_id(ruleset_id) {}
 
 		virtual ~ruleset_filters() {};