diff --git a/scrapy/utils/project.py b/scrapy/utils/project.py
index 95c6a8035..1cbda141a 100644
--- a/scrapy/utils/project.py
+++ b/scrapy/utils/project.py
@@ -8,6 +8,7 @@ from os.path import join, dirname, abspath, isabs, exists
 from scrapy.utils.conf import closest_scrapy_cfg, get_config, init_env
 from scrapy.settings import Settings
 from scrapy.exceptions import NotConfigured
+from scrapy.exceptions import ScrapyDeprecationWarning
 
 ENVVAR = 'SCRAPY_SETTINGS_MODULE'
 DATADIR_CFG_SECTION = 'datadir'
@@ -70,6 +71,9 @@ def get_project_settings():
     # XXX: remove this hack
     pickled_settings = os.environ.get("SCRAPY_PICKLED_SETTINGS_TO_OVERRIDE")
     if pickled_settings:
+        warnings.warn("Use of environment variable "
+                      "'SCRAPY_PICKLED_SETTINGS_TO_OVERRIDE' "
+                      "is deprecated.", ScrapyDeprecationWarning)
         settings.setdict(pickle.loads(pickled_settings), priority='project')
 
     # XXX: deprecate and remove this functionality