diff --git a/src/vector.h b/src/vector.h
index d8dd8c6..536b0f3 100644
--- a/src/vector.h
+++ b/src/vector.h
@@ -2,8 +2,8 @@
 #define PHP_DLIB_VECTOR_H
 
 ZEND_BEGIN_ARG_INFO_EX(dlib_vector_length_arginfo, 0, 0, 2)
-    ZEND_ARG_INFO(0, x_arg)
-    ZEND_ARG_INFO(0, y_arg)
+    ZEND_ARG_INFO(1, x_arg)
+    ZEND_ARG_INFO(1, y_arg)
 ZEND_END_ARG_INFO()
 PHP_FUNCTION(dlib_vector_length);
 
diff --git a/tests/vector_length.phpt b/tests/vector_length.phpt
index c840d49..60b4747 100644
--- a/tests/vector_length.phpt
+++ b/tests/vector_length.phpt
@@ -4,9 +4,15 @@ Basic tests for dlib_vector_length
 <?php if (!extension_loaded("pdlib")) print "skip"; ?>
 --FILE--
 <?php
-var_dump(dlib_vector_length([0.0, 0.0],       [1.0, 0.0]));
-var_dump(dlib_vector_length([0.0, 0.0, -1.0], [0.0, 0.0, 1.0]));
-var_dump(dlib_vector_length([0.0, 2.5,  1.0], [0.0, 1.0, 1.0]));
+$vectorAL = [0.0, 0.0];
+$vectorAR = [0.0, 1.0];
+var_dump(dlib_vector_length($vectorAL, $vectorAR));
+$vectorBL = [0.0, 0.0, -1.0];
+$vectorBR = [0.0, 0.0, 1.0];
+var_dump(dlib_vector_length($vectorBL, $vectorBR));
+$vectorCL = [0.0, 2.5, 1.0];
+$vectorCR = [0.0, 1.0, 1.0];
+var_dump(dlib_vector_length($vectorCL, $vectorCR));
 ?>
 --EXPECT--
 float(1)