diff --git a/src/counterfactuals/flatten.jl b/src/counterfactuals/flatten.jl
index 28754ae14..6498f4576 100644
--- a/src/counterfactuals/flatten.jl
+++ b/src/counterfactuals/flatten.jl
@@ -51,4 +51,4 @@ Returns the encoded representation of `flat_ce.target`.
 """
 function target_encoded(flat_ce::FlattenedCE, data::CounterfactualData)
     return data.output_encoder(flat_ce.target; y_levels=data.y_levels)
-end
\ No newline at end of file
+end
diff --git a/src/counterfactuals/utils.jl b/src/counterfactuals/utils.jl
index ca981046d..3e1e2ee59 100644
--- a/src/counterfactuals/utils.jl
+++ b/src/counterfactuals/utils.jl
@@ -96,4 +96,5 @@ end
 
 Overloads the function for [`CounterfactualExplanation`](@ref) to use the counterfactual data's labels if no data is provided.
 """
-find_potential_neighbours(ce::CounterfactualExplanation, n::Int=1000) = find_potential_neighbours(ce, ce.data, n)
+find_potential_neighbours(ce::CounterfactualExplanation, n::Int=1000) =
+    find_potential_neighbours(ce, ce.data, n)
diff --git a/src/objectives/penalties.jl b/src/objectives/penalties.jl
index 392eb7303..ebb2b37a7 100644
--- a/src/objectives/penalties.jl
+++ b/src/objectives/penalties.jl
@@ -121,11 +121,13 @@ function distance_from_target(
 )
 
     # Get potential neighbours:
-    get!(
-        ce.search,
-        :potential_neighbours,
-        CounterfactualExplanations.find_potential_neighbours(ce, K),
-    )
+    ChainRulesCore.ignore_derivatives() do
+        get!(
+            ce.search,
+            :potential_neighbours,
+            CounterfactualExplanations.find_potential_neighbours(ce, K),
+        )
+    end
 
     ys = ce.search[:potential_neighbours]
     if K > size(ys, 2)