diff --git a/mitogen/ssh.py b/mitogen/ssh.py
index 656dc72c..6e6e04f9 100644
--- a/mitogen/ssh.py
+++ b/mitogen/ssh.py
@@ -213,6 +213,8 @@ class Options(mitogen.parent.Options):
         if ssh_path:
             self.ssh_path = ssh_path
         if ssh_args:
+            if not isinstance(ssh_args, list):
+                raise ValueError('ssh_args expected to be a list')
             self.ssh_args = ssh_args
         if ssh_debug_level:
             self.ssh_debug_level = ssh_debug_level