diff --git a/requirements.txt b/requirements.txt
index e95d2d3e3..3e8fb4911 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,5 @@
 boto3==1.7.4
+ply==3.8 # required by google-gax
 google-compute-engine>=2.4.1 #required by boto
 configparser>=3.5.0
 zc.lockfile>=1.2.1
diff --git a/setup.py b/setup.py
index 298d45953..1417ee58d 100644
--- a/setup.py
+++ b/setup.py
@@ -6,6 +6,7 @@ from dvc import VERSION
 
 install_requires = [
     "boto3==1.7.4",
+    "ply==3.8", #required by google-gax
     "google-compute-engine>=2.4.1", #required by boto
     "configparser>=3.5.0",
     "zc.lockfile>=1.2.1",