diff --git a/torchattack/att.py b/torchattack/att.py
index 0901ffe..0b2a2fc 100644
--- a/torchattack/att.py
+++ b/torchattack/att.py
@@ -56,7 +56,7 @@ def __init__(
         if hook_cfg:
             # Explicit config name takes precedence over inferred model.model_name
             self.hook_cfg = hook_cfg
-        elif hasattr(model, 'model_name'):
+        elif isinstance(model, AttackModel):
             # If model is initialized via `torchattack.AttackModel`, the model_name
             # is automatically attached to the model during instantiation.
             self.hook_cfg = model.model_name
diff --git a/torchattack/dr.py b/torchattack/dr.py
index 5585045..85caee6 100644
--- a/torchattack/dr.py
+++ b/torchattack/dr.py
@@ -56,7 +56,7 @@ def __init__(
 
         # If model is initialized via `torchattack.AttackModel`, infer its model_name
         # from automatically attached attribute during instantiation.
-        if not model_name and hasattr(model, 'model_name'):
+        if not model_name and isinstance(model, AttackModel):
             model_name = model.model_name
 
         self.eps = eps
diff --git a/torchattack/pna_patchout.py b/torchattack/pna_patchout.py
index 10ca34d..61261bc 100644
--- a/torchattack/pna_patchout.py
+++ b/torchattack/pna_patchout.py
@@ -59,7 +59,7 @@ def __init__(
         if hook_cfg:
             # Explicit config name takes precedence over inferred model.model_name
             self.hook_cfg = hook_cfg
-        elif hasattr(model, 'model_name'):
+        elif isinstance(model, AttackModel):
             # If model is initialized via `torchattack.AttackModel`, the model_name
             # is automatically attached to the model during instantiation.
             self.hook_cfg = model.model_name
diff --git a/torchattack/tgr.py b/torchattack/tgr.py
index 081464b..e1f7d73 100644
--- a/torchattack/tgr.py
+++ b/torchattack/tgr.py
@@ -55,7 +55,7 @@ def __init__(
         if hook_cfg:
             # Explicit config name takes precedence over inferred model.model_name
             self.hook_cfg = hook_cfg
-        elif hasattr(model, 'model_name'):
+        elif isinstance(model, AttackModel):
             # If model is initialized via `torchattack.AttackModel`, the model_name
             # is automatically attached to the model during instantiation.
             self.hook_cfg = model.model_name
diff --git a/torchattack/vdc.py b/torchattack/vdc.py
index de644e4..66dc11b 100644
--- a/torchattack/vdc.py
+++ b/torchattack/vdc.py
@@ -57,10 +57,9 @@ def __init__(
         if hook_cfg:
             # Explicit config name takes precedence over inferred model.model_name
             self.hook_cfg = hook_cfg
-        elif hasattr(model, 'model_name'):
+        elif isinstance(model, AttackModel):
             # If model is initialized via `torchattack.AttackModel`, the model_name
             # is automatically attached to the model during instantiation.
-            assert isinstance(str, model.model_name)
             self.hook_cfg = model.model_name
 
         self.eps = eps