diff --git a/include/assimp/vector3.h b/include/assimp/vector3.h
index 7b5269c9c..584a50835 100644
--- a/include/assimp/vector3.h
+++ b/include/assimp/vector3.h
@@ -88,6 +88,7 @@ public:
 	// comparison
 	bool operator== (const aiVector3t& other) const;
 	bool operator!= (const aiVector3t& other) const;
+	bool operator < (const aiVector3t& other) const;
 
 	template <typename TOther>
 	operator aiVector3t<TOther> () const;