diff --git a/Math/Matrix.php b/Math/Matrix.php
index c07f4c6..2eb6d78 100644
--- a/Math/Matrix.php
+++ b/Math/Matrix.php
@@ -1163,7 +1163,8 @@ function multiply(&$B) {
      * @throws InvalidArgumentException
      */
     function &vectorMultiply(&$v1) {
-        if (!Math_VectorOp::isVector($v1)) {
+        $validator = new Math_VectorOp();
+        if (!$validator->isVector($v1)) {
             throw new InvalidArgumentException("Wrong parameter, a Math_Vector object");
         }
         list($nr, $nc) = $this->getSize();