diff --git a/src/interp1d/strategies/cubic_spline.rs b/src/interp1d/strategies/cubic_spline.rs
index b8c5437..58fe474 100644
--- a/src/interp1d/strategies/cubic_spline.rs
+++ b/src/interp1d/strategies/cubic_spline.rs
@@ -287,8 +287,14 @@ where
             BoundaryCondition::Clamped => Self::solve_for_k(kv, x, data, RowBoundary::Clamped),
             BoundaryCondition::NotAKnot => Self::solve_for_k(kv, x, data, RowBoundary::NotAKnot),
             BoundaryCondition::Individual(bounds) => {
-                assert!(kv.raw_dim().remove_axis(AX0) == bounds.raw_dim().remove_axis(AX0)); // TODO: return error
-                assert!(bounds.raw_dim()[0] == 1); // TODO: return error
+                let mut bounds_shape = kv.raw_dim();
+                bounds_shape[0] = 1;
+                if bounds_shape != bounds.raw_dim() {
+                    return Err(BuilderError::ShapeError(format!(
+                        "Boundary conditions array has wrong shape. Expected: {bounds_shape:?}, got: {:?}",
+                        bounds.raw_dim()
+                    )));
+                }
                 Self::solve_for_k_individual(
                     kv.into_dyn(),
                     x,
diff --git a/tests/cubic_spline_strat.rs b/tests/cubic_spline_strat.rs
index 59eea88..1b567fd 100644
--- a/tests/cubic_spline_strat.rs
+++ b/tests/cubic_spline_strat.rs
@@ -409,3 +409,32 @@ fn extrapolate_deriv2() {
     ];
     assert_relative_eq!(res, expect, epsilon = f64::EPSILON, max_relative = 0.001);
 }
+
+#[test]
+#[should_panic(expected = "Expected: [1, 2], got: [1, 3]")]
+fn bounds_shape_error1() {
+    let y = array![[0.5, 1.0], [0.0, 1.5], [3.0, 0.5],];
+    let boundaries = BoundaryCondition::Individual(array![[
+        RowBoundary::Natural,
+        RowBoundary::Periodic,
+        RowBoundary::NotAKnot
+    ],]);
+    Interp1DBuilder::new(y)
+        .strategy(CubicSpline::new().boundary(boundaries))
+        .build()
+        .unwrap();
+}
+
+#[test]
+#[should_panic(expected = "Expected: [1, 2], got: [2, 2]")]
+fn bounds_shape_error2() {
+    let y = array![[0.5, 1.0], [0.0, 1.5], [3.0, 0.5],];
+    let boundaries = BoundaryCondition::Individual(array![
+        [RowBoundary::Natural, RowBoundary::NotAKnot],
+        [RowBoundary::Natural, RowBoundary::NotAKnot],
+    ]);
+    Interp1DBuilder::new(y)
+        .strategy(CubicSpline::new().boundary(boundaries))
+        .build()
+        .unwrap();
+}