diff --git a/ext/tempfile.rb b/ext/tempfile.rb
new file mode 100644
index 00000000..f9a5a014
--- /dev/null
+++ b/ext/tempfile.rb
@@ -0,0 +1,7 @@
+class Tempfile
+  alias_method :size_original, :size
+  def size
+    s = size_original
+    s.nil? ? 0 : s
+  end
+end
diff --git a/tests/tempfile_tests.rb b/tests/tempfile_tests.rb
new file mode 100644
index 00000000..ade275f6
--- /dev/null
+++ b/tests/tempfile_tests.rb
@@ -0,0 +1,10 @@
+require_relative './environment.rb'
+
+describe Tempfile do
+  it 'should return 0 when no data is written' do
+    tmp = Tempfile.new
+    tmp.write ''
+    tmp.close
+    tmp.size.must_equal 0
+  end
+end