diff --git a/lib/rack/test/uploaded_file.rb b/lib/rack/test/uploaded_file.rb
index 5be6dc7..3fd5972 100644
--- a/lib/rack/test/uploaded_file.rb
+++ b/lib/rack/test/uploaded_file.rb
@@ -60,12 +60,13 @@ def method_missing(method_name, *args, &block)
       def append_to(buffer)
         tempfile.rewind
 
-        buf = String.new
-        buffer << tempfile.readpartial(65_536, buf) until tempfile.eof?
-
-        tempfile.rewind
-
-        nil
+        begin
+          buf = String.new
+          buffer << tempfile.readpartial(65_536, buf) until tempfile.eof?
+          nil
+        ensure
+          tempfile.rewind
+        end
       end
 
       def respond_to_missing?(method_name, include_private = false) #:nodoc:
diff --git a/spec/rack/test/uploaded_file_spec.rb b/spec/rack/test/uploaded_file_spec.rb
index 1b2980e..82e3b60 100644
--- a/spec/rack/test/uploaded_file_spec.rb
+++ b/spec/rack/test/uploaded_file_spec.rb
@@ -7,6 +7,20 @@ def file_path
     File.dirname(__FILE__) + '/../../fixtures/foo.txt'
   end
 
+  it 'rewinds after appending raises' do
+    uploaded_file = Rack::Test::UploadedFile.new(
+      StringIO.new('content'),
+      original_filename: 'content.txt'
+    )
+    buffer = Object.new
+    def buffer.<<(_chunk)
+      raise IOError, 'append failed'
+    end
+
+    proc { uploaded_file.append_to(buffer) }.must_raise(IOError)
+    uploaded_file.pos.must_equal 0
+  end
+
   it 'returns an instance of `Rack::Test::UploadedFile`' do
     uploaded_file = Rack::Test::UploadedFile.new(file_path)