diff --git a/scrapypuppeteer/middleware.py b/scrapypuppeteer/middleware.py
index f6c5852..4063e98 100644
--- a/scrapypuppeteer/middleware.py
+++ b/scrapypuppeteer/middleware.py
@@ -156,7 +156,9 @@ def process_response(self, request, response, spider):
         response_cls = self._get_response_class(puppeteer_request.action)
 
         if response.status != 200:
-            self.used_contexts[id(spider)].add(response_data['contextId'])
+            context_id = response_data.get('contextId')
+            if context_id:
+                self.used_contexts[id(spider)].add(context_id)
             return response
 
         return self._form_response(response_cls, response_data,
diff --git a/setup.py b/setup.py
index 185ef43..1b8503f 100644
--- a/setup.py
+++ b/setup.py
@@ -7,7 +7,7 @@
 
 setup(
     name='scrapy-puppeteer-client',
-    version='0.1.3',
+    version='0.1.4',
     description='A library to use Puppeteer-managed browser in Scrapy spiders',
     long_description=long_description,
     long_description_content_type="text/markdown",