diff --git a/keras/src/applications/densenet.py b/keras/src/applications/densenet.py
index 436401d258bf..faa8fa2265b3 100644
--- a/keras/src/applications/densenet.py
+++ b/keras/src/applications/densenet.py
@@ -487,6 +487,6 @@ def decode_predictions(preds, top=5):
     A Keras model instance.
 """
 
-setattr(DenseNet121, "__doc__", DenseNet121.__doc__ + DOC)
-setattr(DenseNet169, "__doc__", DenseNet169.__doc__ + DOC)
-setattr(DenseNet201, "__doc__", DenseNet201.__doc__ + DOC)
+setattr(DenseNet121, "__doc__", (DenseNet121.__doc__ or "") + DOC)
+setattr(DenseNet169, "__doc__", (DenseNet169.__doc__ or "") + DOC)
+setattr(DenseNet201, "__doc__", (DenseNet201.__doc__ or "") + DOC)
diff --git a/keras/src/applications/resnet.py b/keras/src/applications/resnet.py
index 0948f8901db1..6385da280a69 100644
--- a/keras/src/applications/resnet.py
+++ b/keras/src/applications/resnet.py
@@ -586,6 +586,7 @@ def decode_predictions(preds, top=5):
     A Model instance.
 """
 
-setattr(ResNet50, "__doc__", ResNet50.__doc__ + DOC)
-setattr(ResNet101, "__doc__", ResNet101.__doc__ + DOC)
-setattr(ResNet152, "__doc__", ResNet152.__doc__ + DOC)
+if ResNet50.__doc__ is not None:
+    setattr(ResNet50, "__doc__", ResNet50.__doc__ + DOC)
+    setattr(ResNet101, "__doc__", ResNet101.__doc__ + DOC)
+    setattr(ResNet152, "__doc__", ResNet152.__doc__ + DOC)
diff --git a/keras/src/applications/resnet_v2.py b/keras/src/applications/resnet_v2.py
index 590efa0bbbda..4983281a4014 100644
--- a/keras/src/applications/resnet_v2.py
+++ b/keras/src/applications/resnet_v2.py
@@ -203,6 +203,7 @@ def decode_predictions(preds, top=5):
     A Model instance.
 """
 
-setattr(ResNet50V2, "__doc__", ResNet50V2.__doc__ + DOC)
-setattr(ResNet101V2, "__doc__", ResNet101V2.__doc__ + DOC)
-setattr(ResNet152V2, "__doc__", ResNet152V2.__doc__ + DOC)
+if ResNet50V2.__doc__ is not None:
+    setattr(ResNet50V2, "__doc__", ResNet50V2.__doc__ + DOC)
+    setattr(ResNet101V2, "__doc__", ResNet101V2.__doc__ + DOC)
+    setattr(ResNet152V2, "__doc__", ResNet152V2.__doc__ + DOC)
diff --git a/keras/src/optimizers/adadelta.py b/keras/src/optimizers/adadelta.py
index 7e5a450ecbfa..9b662f05ec00 100644
--- a/keras/src/optimizers/adadelta.py
+++ b/keras/src/optimizers/adadelta.py
@@ -130,6 +130,7 @@ def get_config(self):
         return config
 
 
-Adadelta.__doc__ = Adadelta.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if Adadelta.__doc__ is not None:
+    Adadelta.__doc__ = Adadelta.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/adafactor.py b/keras/src/optimizers/adafactor.py
index 54fd74d1e783..b0f59cff6a3c 100644
--- a/keras/src/optimizers/adafactor.py
+++ b/keras/src/optimizers/adafactor.py
@@ -209,6 +209,7 @@ def get_config(self):
         return config
 
 
-Adafactor.__doc__ = Adafactor.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if Adafactor.__doc__ is not None:
+    Adafactor.__doc__ = Adafactor.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/adagrad.py b/keras/src/optimizers/adagrad.py
index 1323bc1027ea..55f05d2fa835 100644
--- a/keras/src/optimizers/adagrad.py
+++ b/keras/src/optimizers/adagrad.py
@@ -103,6 +103,7 @@ def get_config(self):
         return config
 
 
-Adagrad.__doc__ = Adagrad.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if Adagrad.__doc__ is not None:
+    Adagrad.__doc__ = Adagrad.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/adam.py b/keras/src/optimizers/adam.py
index 2c3970e97aa4..1541dafac604 100644
--- a/keras/src/optimizers/adam.py
+++ b/keras/src/optimizers/adam.py
@@ -149,6 +149,7 @@ def get_config(self):
         return config
 
 
-Adam.__doc__ = Adam.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if Adam.__doc__ is not None:
+    Adam.__doc__ = Adam.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/adamax.py b/keras/src/optimizers/adamax.py
index 661fe1cb5310..b6967d0ee6ad 100644
--- a/keras/src/optimizers/adamax.py
+++ b/keras/src/optimizers/adamax.py
@@ -141,6 +141,7 @@ def get_config(self):
         return config
 
 
-Adamax.__doc__ = Adamax.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if Adamax.__doc__ is not None:
+    Adamax.__doc__ = Adamax.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/adamw.py b/keras/src/optimizers/adamw.py
index 9db4a30094ab..54cfe452bfbb 100644
--- a/keras/src/optimizers/adamw.py
+++ b/keras/src/optimizers/adamw.py
@@ -95,6 +95,7 @@ def __init__(
             )
 
 
-AdamW.__doc__ = AdamW.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if AdamW.__doc__ is not None:
+    AdamW.__doc__ = AdamW.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/ftrl.py b/keras/src/optimizers/ftrl.py
index 6bef848a905b..379a435d038c 100644
--- a/keras/src/optimizers/ftrl.py
+++ b/keras/src/optimizers/ftrl.py
@@ -234,6 +234,7 @@ def get_config(self):
         return config
 
 
-Ftrl.__doc__ = Ftrl.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if Ftrl.__doc__ is not None:
+    Ftrl.__doc__ = Ftrl.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/lamb.py b/keras/src/optimizers/lamb.py
index 5a4e1f3958d5..a697ce6d1d46 100644
--- a/keras/src/optimizers/lamb.py
+++ b/keras/src/optimizers/lamb.py
@@ -143,6 +143,7 @@ def get_config(self):
         return config
 
 
-Lamb.__doc__ = Lamb.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if Lamb.__doc__ is not None:
+    Lamb.__doc__ = Lamb.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/lion.py b/keras/src/optimizers/lion.py
index 5c798eb71355..6d1c66126527 100644
--- a/keras/src/optimizers/lion.py
+++ b/keras/src/optimizers/lion.py
@@ -131,6 +131,7 @@ def get_config(self):
         return config
 
 
-Lion.__doc__ = Lion.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if Lion.__doc__ is not None:
+    Lion.__doc__ = Lion.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/loss_scale_optimizer.py b/keras/src/optimizers/loss_scale_optimizer.py
index 1b9945c4157b..34f662236e0a 100644
--- a/keras/src/optimizers/loss_scale_optimizer.py
+++ b/keras/src/optimizers/loss_scale_optimizer.py
@@ -307,6 +307,7 @@ def from_config(cls, config, custom_objects=None):
         return cls(inner_optimizer, **config)
 
 
-LossScaleOptimizer.__doc__ = LossScaleOptimizer.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if LossScaleOptimizer.__doc__ is not None:
+    LossScaleOptimizer.__doc__ = LossScaleOptimizer.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/nadam.py b/keras/src/optimizers/nadam.py
index 4b0fddb83b19..bf9ef3be89f8 100644
--- a/keras/src/optimizers/nadam.py
+++ b/keras/src/optimizers/nadam.py
@@ -158,6 +158,7 @@ def get_config(self):
         return config
 
 
-Nadam.__doc__ = Nadam.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if Nadam.__doc__ is not None:
+    Nadam.__doc__ = Nadam.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/rmsprop.py b/keras/src/optimizers/rmsprop.py
index b32b5b61d6b9..f98309d9047a 100644
--- a/keras/src/optimizers/rmsprop.py
+++ b/keras/src/optimizers/rmsprop.py
@@ -167,6 +167,7 @@ def get_config(self):
         return config
 
 
-RMSprop.__doc__ = RMSprop.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if RMSprop.__doc__ is not None:
+    RMSprop.__doc__ = RMSprop.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )
diff --git a/keras/src/optimizers/sgd.py b/keras/src/optimizers/sgd.py
index 15c951ed8d06..55c4b62e96cd 100644
--- a/keras/src/optimizers/sgd.py
+++ b/keras/src/optimizers/sgd.py
@@ -133,6 +133,7 @@ def get_config(self):
         return config
 
 
-SGD.__doc__ = SGD.__doc__.replace(
-    "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
-)
+if SGD.__doc__ is not None:
+    SGD.__doc__ = SGD.__doc__.replace(
+        "{{base_optimizer_keyword_args}}", optimizer.base_optimizer_keyword_args
+    )