diff --git a/pertpy/tools/_perturbation_space/_perturbation_space.py b/pertpy/tools/_perturbation_space/_perturbation_space.py
index 026fdea0..4336623d 100644
--- a/pertpy/tools/_perturbation_space/_perturbation_space.py
+++ b/pertpy/tools/_perturbation_space/_perturbation_space.py
@@ -233,11 +233,15 @@ def add(
         new_perturbation.obs = new_obs
 
         for key, value in data["layers"].items():
-            key_name = key.removesuffix("_control_diff") if key.endswith("_control_diff") else key
+            key_name = (
+                key.removesuffix("_control_diff") if isinstance(key, str) and key.endswith("_control_diff") else key
+            )
             new_perturbation.layers[key_name] = value
 
         for key, value in data["embeddings"].items():
-            key_name = key.removesuffix("_control_diff") if key.endswith("_control_diff") else key
+            key_name = (
+                key.removesuffix("_control_diff") if isinstance(key, str) and key.endswith("_control_diff") else key
+            )
             new_perturbation.obsm[key_name] = value
 
         new_perturbation.obs[target_col] = new_perturbation.obs_names.astype("category")
@@ -336,11 +340,15 @@ def subtract(
         new_perturbation.obs = new_obs
 
         for key, value in data["layers"].items():
-            key_name = key.removesuffix("_control_diff") if key.endswith("_control_diff") else key
+            key_name = (
+                key.removesuffix("_control_diff") if isinstance(key, str) and key.endswith("_control_diff") else key
+            )
             new_perturbation.layers[key_name] = value
 
         for key, value in data["embeddings"].items():
-            key_name = key.removesuffix("_control_diff") if key.endswith("_control_diff") else key
+            key_name = (
+                key.removesuffix("_control_diff") if isinstance(key, str) and key.endswith("_control_diff") else key
+            )
             new_perturbation.obsm[key_name] = value
 
         new_perturbation.obs[target_col] = new_perturbation.obs_names.astype("category")
diff --git a/pertpy/tools/_perturbation_space/_simple.py b/pertpy/tools/_perturbation_space/_simple.py
index 6db0374a..5f8f3d95 100644
--- a/pertpy/tools/_perturbation_space/_simple.py
+++ b/pertpy/tools/_perturbation_space/_simple.py
@@ -171,6 +171,9 @@ def compute(
         if mode in ps_adata.layers:
             ps_adata.X = ps_adata.layers[mode]
 
+        if None in ps_adata.layers:
+            del ps_adata.layers[None]
+
         missing_cols = [col for col in original_obs.columns if col not in ps_adata.obs.columns]
         new_cols_data = {}