diff --git a/requirements.txt b/requirements.txt
index d6e2c66da3..938a5ef762 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 boto3==1.7.4
-ply==3.8 # required by google-gax
+ply>=3.9 # See https://github.com/pyinstaller/pyinstaller/issues/1945
 configparser>=3.5.0
 zc.lockfile>=1.2.1
 future>=0.16.0
diff --git a/setup.py b/setup.py
index c4ae9963b0..f6b2e6886e 100644
--- a/setup.py
+++ b/setup.py
@@ -5,7 +5,7 @@
 
 
 install_requires = [
-    "ply==3.8", # required by google-gax
+    "ply>=3.9", # See https://github.com/pyinstaller/pyinstaller/issues/1945
     "configparser>=3.5.0",
     "zc.lockfile>=1.2.1",
     "future>=0.16.0",