diff --git a/README.rst b/README.rst
index db16a4ba..60342174 100644
--- a/README.rst
+++ b/README.rst
@@ -38,6 +38,7 @@ Some functionalities of ryu requires extra packages:
 - OF-Config requires lxml and ncclient
 - NETCONF requires paramiko
 - BGP speaker (SSH console) requires paramiko
+- Zebra protocol service (database) requires SQLAlchemy
 
 If you want to use the functionalities, please install requirements::
 
diff --git a/tools/optional-requires b/tools/optional-requires
index 36c89ec0..1bc4cce7 100644
--- a/tools/optional-requires
+++ b/tools/optional-requires
@@ -2,3 +2,4 @@ lxml!=3.7.0,>=2.3    # OF-Config
 ncclient  # OF-Config
 cryptography!=1.5.2  # Required by paramiko
 paramiko  # NETCONF, BGP speaker (SSH console)
+SQLAlchemy>=1.0.10,<1.1.0  # Zebra protocol service