diff --git a/chainerrl_visualizer/launcher.py b/chainerrl_visualizer/launcher.py
index cec6b9d..eebf17d 100644
--- a/chainerrl_visualizer/launcher.py
+++ b/chainerrl_visualizer/launcher.py
@@ -110,6 +110,13 @@ def inspect_agent(agent, gymlike_env, contains_rnn):
     model = agent.model
     obs = gymlike_env.reset()
 
+    # workaround
+    # The author of this library (@sykwer) assumed that all agents have a `model` attribute and
+    # `model.__call__()` returns outputs of the model. However, DDPG, PGT and TRPO are exceptions
+    # for the assumption. This issue will be fixed soon.
+    if type(agent).__name__ in ['DDPG', 'PGT', 'TRPO']:
+        raise Exception('Agent type of {} is not supported for now'.format(type(agent).__name__))
+
     # workaround
     if hasattr(agent, 'xp'):
         xp = agent.xp