diff --git a/src/cryojax/data/_relion.py b/src/cryojax/data/_relion.py
index 35da8a88..d220cab0 100644
--- a/src/cryojax/data/_relion.py
+++ b/src/cryojax/data/_relion.py
@@ -246,14 +246,16 @@ def _get_starfile_params(
             jnp.asarray(voltage_in_kilovolts, device=device),
         )
         # ... now the ContrastTransferTheory
-        make_ctf = lambda params: ContrastTransferFunction(
-            defocus_in_angstroms=params[0],
-            astigmatism_in_angstroms=params[1],
-            astigmatism_angle=params[2],
-            voltage_in_kilovolts=params[3],
-            spherical_aberration_in_mm=params[4],
-            amplitude_contrast_ratio=params[5],
-            phase_shift=params[6],
+        make_ctf = (
+            lambda defocus, astig, angle, voltage, sph, ac, ps: ContrastTransferFunction(
+                defocus_in_angstroms=defocus,
+                astigmatism_in_angstroms=astig,
+                astigmatism_angle=angle,
+                voltage_in_kilovolts=voltage,
+                spherical_aberration_in_mm=sph,
+                amplitude_contrast_ratio=ac,
+                phase_shift=ps,
+            )
         )
         ctf_params = (
             defocus_in_angstroms,
@@ -265,9 +267,9 @@ def _get_starfile_params(
             phase_shift,
         )
         ctf = (
-            eqx.filter_vmap(make_ctf, in_axes=(0, 0, 0, None, None, None, 0))(ctf_params)
+            eqx.filter_vmap(make_ctf, in_axes=(0, 0, 0, None, None, None, 0))(*ctf_params)
             if defocus_in_angstroms.ndim == 1
-            else make_ctf(ctf_params)
+            else make_ctf(*ctf_params)
         )
         if self.get_envelope_function:
             b_factor, scale_factor = (
@@ -282,14 +284,12 @@ def _get_starfile_params(
                     else jnp.asarray(1.0)
                 ),
             )
-            make_envelope = lambda params: FourierGaussian(
-                b_factor=params[0], amplitude=params[1]
-            )
+            make_envelope = lambda b, amp: FourierGaussian(b_factor=b, amplitude=amp)
             envelope_params = (b_factor, scale_factor)
             envelope = (
-                eqx.filter_vmap(make_envelope, in_axes=(0, 0))(envelope_params)
+                eqx.filter_vmap(make_envelope, in_axes=(0, 0))(*envelope_params)
                 if b_factor.ndim == 1
-                else make_envelope(envelope_params)
+                else make_envelope(*envelope_params)
             )
         else:
             envelope = None