diff --git a/src/testdir/test_channel.py b/src/testdir/test_channel.py
index a465d65..47a12ea 100644
--- a/src/testdir/test_channel.py
+++ b/src/testdir/test_channel.py
@@ -104,6 +104,11 @@
                         print("sending: {}".format(cmd))
                         self.request.sendall(cmd.encode('utf-8'))
                         response = "ok"
+                    elif decoded[1] == 'malformed':
+                        cmd = '["ex",":"]wrong!["ex","smi"]'
+                        print("sending: {}".format(cmd))
+                        self.request.sendall(cmd.encode('utf-8'))
+                        response = "ok"
                     elif decoded[1] == 'an expr':
                         # Send an expr request.
                         cmd = '["expr","setline(\\"$\\", [\\"one\\",\\"two\\",\\"three\\"])"]'