diff --git a/doc/source/configure.rst b/doc/source/configure.rst
index a5c4b4c41..2c8bac625 100644
--- a/doc/source/configure.rst
+++ b/doc/source/configure.rst
@@ -116,6 +116,9 @@ behind a firewall, this feature is useful for instances exposed to the internet
 where configuring a firewall is not possible. Because Redis is
 very fast at serving queries, the chosen password should be long.
 
+
+.. note:: The Redis passwords provided below may not contain spaces.
+
 Redis authentication is only supported on the raylet code path.
 
 To add authentication via the Python API, start Ray using:
diff --git a/python/ray/services.py b/python/ray/services.py
index 5b806f8dc..e4247d7f2 100644
--- a/python/ray/services.py
+++ b/python/ray/services.py
@@ -772,6 +772,8 @@ def _start_redis_instance(executable,
         # Construct the command to start the Redis server.
         command = [executable]
         if password:
+            if " " in password:
+                raise ValueError("Spaces not permitted in redis password.")
             command += ["--requirepass", password]
         command += (
             ["--port", str(port), "--loglevel", "warning"] + load_module_args)