diff --git a/scrapy/pipelines/files.py b/scrapy/pipelines/files.py
index ab18a727d..af1d5488a 100644
--- a/scrapy/pipelines/files.py
+++ b/scrapy/pipelines/files.py
@@ -207,6 +207,8 @@ class GCSFilesStore(object):
     GCS_PROJECT_ID = None
 
     CACHE_CONTROL = 'max-age=172800'
+    POLICY = 'projectPrivate'  # Overriden from settings.FILES_STORE_GCS_ACL in
+                               # FilesPipeline.from_settings.
 
     def __init__(self, uri):
         from google.cloud import storage
@@ -239,7 +241,8 @@ class GCSFilesStore(object):
         return threads.deferToThread(
             blob.upload_from_string,
             data=buf.getvalue(),
-            content_type=self._get_content_type(headers)
+            content_type=self._get_content_type(headers),
+            predefined_acl=self.POLICY
         )
 
 
@@ -314,6 +317,7 @@ class FilesPipeline(MediaPipeline):
 
         gcs_store = cls.STORE_SCHEMES['gs']
         gcs_store.GCS_PROJECT_ID = settings['GCS_PROJECT_ID']
+        gcs_store.POLICY = settings['FILES_STORE_GCS_ACL']
 
         store_uri = settings['FILES_STORE']
         return cls(store_uri, settings=settings)
diff --git a/scrapy/pipelines/images.py b/scrapy/pipelines/images.py
index c5fc12afe..5cdddce49 100644
--- a/scrapy/pipelines/images.py
+++ b/scrapy/pipelines/images.py
@@ -93,6 +93,7 @@ class ImagesPipeline(FilesPipeline):
 
         gcs_store = cls.STORE_SCHEMES['gs']
         gcs_store.GCS_PROJECT_ID = settings['GCS_PROJECT_ID']
+        gcs_store.POLICY = settings['IMAGES_STORE_GCS_ACL']
 
         store_uri = settings['IMAGES_STORE']
         return cls(store_uri, settings=settings)
diff --git a/scrapy/settings/default_settings.py b/scrapy/settings/default_settings.py
index ead511473..7916b9704 100644
--- a/scrapy/settings/default_settings.py
+++ b/scrapy/settings/default_settings.py
@@ -159,6 +159,7 @@ FEED_EXPORTERS_BASE = {
 FEED_EXPORT_INDENT = 0
 
 FILES_STORE_S3_ACL = 'private'
+FILES_STORE_GCS_ACL = 'projectPrivate'
 
 FTP_USER = 'anonymous'
 FTP_PASSWORD = 'guest'
@@ -181,6 +182,7 @@ HTTPPROXY_ENABLED = True
 HTTPPROXY_AUTH_ENCODING = 'latin-1'
 
 IMAGES_STORE_S3_ACL = 'private'
+IMAGES_STORE_GCS_ACL = 'projectPrivate'
 
 ITEM_PROCESSOR = 'scrapy.pipelines.ItemPipelineManager'