diff --git a/lib/tempfile.rb b/lib/tempfile.rb
index d068dd603c..b36c6638b6 100644
--- a/lib/tempfile.rb
+++ b/lib/tempfile.rb
@@ -227,7 +227,7 @@ class Tempfile < DelegateClass(File)
     if !@tmpfile.closed?
       @tmpfile.size # File#size calls rb_io_flush_raw()
     else
-      File.size?(@tmpfile.path)
+      File.size(@tmpfile.path)
     end
   end
   alias length size
diff --git a/test/test_tempfile.rb b/test/test_tempfile.rb
index 7f7f75c7db..a2b272747e 100644
--- a/test/test_tempfile.rb
+++ b/test/test_tempfile.rb
@@ -247,6 +247,13 @@ puts Tempfile.new('foo').path
     assert_equal 5, t.size
   end
 
+  def test_size_on_empty_file
+    t = tempfile("foo")
+    t.write("")
+    t.close
+    assert_equal 0, t.size
+  end
+
   def test_concurrency
     threads = []
     tempfiles = []