diff --git a/requirements.in b/requirements.in
index 85d093218..1b26ee14c 100644
--- a/requirements.in
+++ b/requirements.in
@@ -36,6 +36,7 @@ mailchimp
 Markdown
 mock
 Pillow  # for sorl-thumbnail
+pylibmc==1.5.2 # Note that memcache on heroku doesn't like the new version, so lock it here.
 pyparsing
 raven
 redis
diff --git a/requirements.txt b/requirements.txt
index eb4a9c3be..9bbc05e0a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -67,7 +67,7 @@ pillow==6.0.0
 psutil==5.6.1             # via django-gulp
 psycopg2==2.8.1           # via django-heroku
 pycparser==2.19           # via cffi
-pylibmc==1.6.0            # via django-pylibmc
+pylibmc==1.5.2
 pyparsing==2.4.0
 python-dateutil==2.8.0    # via arrow, botocore, faker
 python-magic==0.4.15