diff --git a/requirements.txt b/requirements.txt
index fb5a3cf..5c63b5c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 ecdsa>=0.9
-protobuf>=2.6.1
+protobuf==2.6.1
 mnemonic>=0.17
 hidapi>=0.7.99.post20
 requests>=2.4.0
diff --git a/setup.py b/setup.py
index f1b16a1..310704d 100755
--- a/setup.py
+++ b/setup.py
@@ -3,7 +3,7 @@ from setuptools import setup
 
 install_requires = [
     'ecdsa>=0.9',
-    'protobuf>=2.6.1',
+    'protobuf==2.6.1',
     'mnemonic>=0.17',
     'setuptools>=19.0',
     'requests>=2.4.0',