diff --git a/src/Notebook_Processor/desired_state/cell_modifier.py b/src/Notebook_Processor/desired_state/cell_modifier.py
index 03d2a615a710ad968fe1b99db8b19f9aea1c76e5..0cd859b1e5516c24ff8a4f0f6dae5b763521b966 100644
--- a/src/Notebook_Processor/desired_state/cell_modifier.py
+++ b/src/Notebook_Processor/desired_state/cell_modifier.py
@@ -155,13 +155,13 @@ class CellModifier(BaseModel):
         if signature[sig_keys[0]].kind not in (inspect.Parameter.POSITIONAL_ONLY, inspect.Parameter.POSITIONAL_OR_KEYWORD):
             raise ValueError(
                 f"Offending function signature: Action {self.action.__name__} must have the first parameter 'cell' as a positional argument.",
-                f"Found: {sig_keys[0], signature[sig_keys[0]]}",
+                f"Found: {sig_keys[0]}, {signature[sig_keys[0]]}",
                 )
 
         if signature[sig_keys[-1]].kind != inspect.Parameter.VAR_KEYWORD:
             raise ValueError(
                 f"Offending function signature: Action {self.action.__name__} must accept keyword arguments.",
-                f"The last paramter should be '**kwargs', found: {sig_keys[-1], signature[sig_keys[-1]].kind}",
+                f"The last paramter should be '**kwargs', found: {sig_keys[-1]}, {signature[sig_keys[-1]].kind}",
                 )
 
         missing_annotations = [