diff --git a/interpax/_spline.py b/interpax/_spline.py
index c44230d..6013582 100644
--- a/interpax/_spline.py
+++ b/interpax/_spline.py
@@ -1072,23 +1072,14 @@ def derivative1():
 def _make_periodic(xq: jax.Array, x: jax.Array, period: float, axis: int, *arrs):
     """Make arrays periodic along a specified axis."""
     period = abs(period)
-    xq = xq % period
-    x = x % period
+    xq = jnp.where(jnp.logical_or(xq > period, xq < 0), xq % period, xq)
+    x = jnp.where(jnp.logical_or(x > period, x < 0), x % period, x)
     i = jnp.argsort(x)
     x = x[i]
-    x = jnp.concatenate([x[-1:] - period, x, x[:1] + period])
     arrs = list(arrs)
     for k in range(len(arrs)):
         if arrs[k] is not None:
             arrs[k] = jnp.take(arrs[k], i, axis, mode="wrap")
-            arrs[k] = jnp.concatenate(
-                [
-                    jnp.take(arrs[k], jnp.array([-1]), axis),
-                    arrs[k],
-                    jnp.take(arrs[k], jnp.array([0]), axis),
-                ],
-                axis=axis,
-            )
     return (xq, x, *arrs)