diff --git a/requirements.txt b/requirements.txt
index 5a1556c1..9d682e75 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1 +1 @@
-msgpack-python>=0.4.0
+msgpack-python>=0.4.0,<=0.5.6
diff --git a/setup.py b/setup.py
index 763872ca..3478f4bb 100755
--- a/setup.py
+++ b/setup.py
@@ -83,6 +83,6 @@ def find_version(*file_paths):
     cmdclass=cmdclass,
     command_options=command_options,
     install_requires=[
-        'msgpack-python>=0.4',
+        'msgpack-python>=0.4,<=0.5.6',
     ]
 )
diff --git a/tox.ini b/tox.ini
index 2a9f9613..8fb43216 100644
--- a/tox.ini
+++ b/tox.ini
@@ -10,5 +10,5 @@ envlist = py27, py36, pypy
 commands = pytest
 deps =
     pyyaml>=3.10
-    msgpack-python>=0.4.0
+    msgpack-python>=0.4.0,<=0.5.6
     pytest>=3.0.0