diff --git a/lib/coursemology/evaluator.rb b/lib/coursemology/evaluator.rb
index 58c2984..9ae0ae7 100644
--- a/lib/coursemology/evaluator.rb
+++ b/lib/coursemology/evaluator.rb
@@ -17,6 +17,7 @@ module Coursemology::Evaluator
   autoload :Logging
   autoload :Models
   autoload :Services
+  autoload :StringIO
 
   # The logger to use for the client.
   mattr_reader(:logger) { ActiveSupport::Logger.new(STDOUT) }
diff --git a/lib/coursemology/evaluator/models/programming_evaluation.rb b/lib/coursemology/evaluator/models/programming_evaluation.rb
index df5f117..814b121 100644
--- a/lib/coursemology/evaluator/models/programming_evaluation.rb
+++ b/lib/coursemology/evaluator/models/programming_evaluation.rb
@@ -30,7 +30,7 @@ def language=(language)
   def package
     @package ||= begin
       body = plain_request('courses/assessment/programming_evaluations/:id/package', id: id)
-      Package.new(StringIO.new(body))
+      Package.new(Coursemology::Evaluator::StringIO.new(body))
     end
   end
 
diff --git a/lib/coursemology/evaluator/string_io.rb b/lib/coursemology/evaluator/string_io.rb
new file mode 100644
index 0000000..6661210
--- /dev/null
+++ b/lib/coursemology/evaluator/string_io.rb
@@ -0,0 +1,13 @@
+# Adapter for StringIO for compatibility with RubyZip.
+#
+# StringIO does not inherit from IO, so RubyZip does not accept StringIO in place of IO.
+class Coursemology::Evaluator::StringIO < ::StringIO
+  def is_a?(klass)
+    klass == IO || super
+  end
+
+  # RubyZip assumes all IO objects respond to path.
+  def path
+    self
+  end
+end
diff --git a/spec/coursemology/evaluator/cli_spec.rb b/spec/coursemology/evaluator/cli_spec.rb
index f1e3f56..881ec92 100644
--- a/spec/coursemology/evaluator/cli_spec.rb
+++ b/spec/coursemology/evaluator/cli_spec.rb
@@ -46,6 +46,12 @@
           subject
         end
       end
+
+      it 'evaluates the package' do
+        VCR.use_cassette('client/pending_evaluation') do
+          subject
+        end
+      end
     end
   end
 
diff --git a/spec/fixtures/vcr/cassettes/client/pending_evaluation.yml b/spec/fixtures/vcr/cassettes/client/pending_evaluation.yml
new file mode 100644
index 0000000..2fcbe47
--- /dev/null
+++ b/spec/fixtures/vcr/cassettes/client/pending_evaluation.yml
@@ -0,0 +1,165 @@
+---
+http_interactions:
+- request:
+    method: post
+    uri: http://localhost:3000/courses/assessment/programming_evaluations/allocate
+    body:
+      encoding: US-ASCII
+      string: ''
+    headers:
+      User-Agent:
+      - ActiveRestClient/1.2.0
+      Connection:
+      - Keep-Alive
+      Accept:
+      - application/hal+json, application/json;q=0.5
+      X-User-Email:
+      - test@example.org
+      X-User-Token:
+      - YOUR_TOKEN_HERE
+      Content-Type:
+      - application/x-www-form-urlencoded
+  response:
+    status:
+      code: 200
+      message: 
+    headers:
+      x-frame-options:
+      - SAMEORIGIN
+      x-xss-protection:
+      - 1; mode=block
+      x-content-type-options:
+      - nosniff
+      content-type:
+      - application/json; charset=utf-8
+      etag:
+      - W/"ebabb61a52d69a09e40e6cc6b70a3506"
+      cache-control:
+      - max-age=0, private, must-revalidate
+      x-request-id:
+      - 09c81730-af3d-4626-9c90-a86569eec7f0
+      x-runtime:
+      - '1.151567'
+      server:
+      - WEBrick/1.3.1 (Ruby/2.2.4/2015-10-28)
+      date:
+      - Wed, 20 Jan 2016 14:15:30 GMT
+      content-length:
+      - '113'
+      connection:
+      - Keep-Alive
+    body:
+      encoding: UTF-8
+      string: '[{"id":1,"language":"Coursemology::Polyglot::Language::Python::Python2Point7","memory_limit":32,"time_limit":10}]'
+    http_version: 
+  recorded_at: Wed, 20 Jan 2016 14:15:31 GMT
+- request:
+    method: get
+    uri: http://localhost:3000/courses/assessment/programming_evaluations/1/package
+    body:
+      encoding: US-ASCII
+      string: ''
+    headers:
+      User-Agent:
+      - ActiveRestClient/1.2.0
+      Connection:
+      - Keep-Alive
+      Accept:
+      - application/hal+json, application/json;q=0.5
+      X-User-Email:
+      - test@example.org
+      X-User-Token:
+      - YOUR_TOKEN_HERE
+      Content-Type:
+      - application/x-www-form-urlencoded
+  response:
+    status:
+      code: 302
+      message: 
+    headers:
+      x-frame-options:
+      - SAMEORIGIN
+      x-xss-protection:
+      - 1; mode=block
+      x-content-type-options:
+      - nosniff
+      location:
+      - http://localhost:3000/downloads/d20151214-14316-19zacic/programming-import20151214-14316-l6y6yg
+      content-type:
+      - text/html; charset=utf-8
+      cache-control:
+      - no-cache
+      x-request-id:
+      - b3094756-62c4-4ef2-950f-dd36c84a5286
+      x-runtime:
+      - '0.395076'
+      server:
+      - WEBrick/1.3.1 (Ruby/2.2.4/2015-10-28)
+      date:
+      - Wed, 20 Jan 2016 14:15:32 GMT
+      content-length:
+      - '161'
+      connection:
+      - Keep-Alive
+    body:
+      encoding: UTF-8
+      string: <html><body>You are being <a href="http://localhost:3000/downloads/d20151214-14316-19zacic/programming-import20151214-14316-l6y6yg">redirected</a>.</body></html>
+    http_version: 
+  recorded_at: Wed, 20 Jan 2016 14:15:32 GMT
+- request:
+    method: get
+    uri: http://localhost:3000/downloads/d20151214-14316-19zacic/programming-import20151214-14316-l6y6yg
+    body:
+      encoding: US-ASCII
+      string: ''
+    headers:
+      User-Agent:
+      - ActiveRestClient/1.2.0
+      Connection:
+      - Keep-Alive
+      Accept:
+      - application/hal+json, application/json;q=0.5
+      X-User-Email:
+      - test@example.org
+      X-User-Token:
+      - YOUR_TOKEN_HERE
+      Content-Type:
+      - application/x-www-form-urlencoded
+  response:
+    status:
+      code: 200
+      message: 
+    headers:
+      last-modified:
+      - Wed, 20 Jan 2016 09:06:59 GMT
+      content-type:
+      - text/plain
+      content-length:
+      - '669'
+      server:
+      - WEBrick/1.3.1 (Ruby/2.2.4/2015-10-28)
+      date:
+      - Wed, 20 Jan 2016 14:15:33 GMT
+      connection:
+      - Keep-Alive
+    body:
+      encoding: ASCII-8BIT
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+recorded_with: VCR 3.0.0