diff --git a/pybop/plot/problem.py b/pybop/plot/problem.py
index 3a644fb5c..3cc4ba020 100644
--- a/pybop/plot/problem.py
+++ b/pybop/plot/problem.py
@@ -73,7 +73,9 @@ def quick(problem, problem_inputs: Inputs = None, show=True, **layout_kwargs):
         )
         plot_dict.traces.append(target_trace)
 
-        if isinstance(problem, FittingProblem):
+        if isinstance(problem, FittingProblem) and len(model_output[i]) == len(
+            target_output[i]
+        ):
             # Compute the standard deviation as proxy for uncertainty
             plot_dict.sigma = np.std(model_output[i] - target_output[i])