diff --git a/test/transition/size-test.js b/test/transition/size-test.js
index 1aca51f..eb18b18 100644
--- a/test/transition/size-test.js
+++ b/test/transition/size-test.js
@@ -1,4 +1,5 @@
 var tape = require("tape"),
+    jsdom = require("../jsdom"),
     d3_selection = require("d3-selection"),
     d3_transition = require("../../");
 
@@ -6,3 +7,10 @@ tape("transition.size is the same as selection.size", function(test) {
   test.equal(d3_transition.transition.prototype.size, d3_selection.selection.prototype.size);
   test.end();
 });
+
+tape("transition.size() returns the expected value", function(test) {
+  var root = jsdom().documentElement;
+  test.equal(d3_selection.select(root).transition().size(), 1);
+  test.equal(d3_selection.selectAll([null, root]).transition().size(), 1);
+  test.end();
+});