diff --git a/crates/engine/src/tests/lut_files.rs b/crates/engine/src/tests/lut_files.rs
index 57d163b36..0153a9997 100644
--- a/crates/engine/src/tests/lut_files.rs
+++ b/crates/engine/src/tests/lut_files.rs
@@ -186,3 +186,43 @@ fn an_overridden_lut_file_renders_again() {
     write(&overridden, WHITE, 2_000);
     assert_all(centre(&s), 1.0);
 }
+
+/// #3538: OCIO File Transform and a custom OCIO config (and the LUT it names) follow their files
+/// through warm layer caches, and a render notes the config's LUT for the disk cache.
+#[test]
+fn ocio_files_render_again_from_warm_caches() {
+    let dir = tempfile::tempdir().unwrap();
+    let (lut, config, grade) = (dir.path().join("file.cube"), dir.path().join("config.ocio"), dir.path().join("luts/grade.cube"));
+    std::fs::create_dir_all(dir.path().join("luts")).unwrap();
+    write(&lut, BLACK, 1_000);
+    write(&grade, BLACK, 1_000);
+    let text = "ocio_profile_version: 2\nsearch_path: luts\nroles:\n  scene_linear: lin\ncolorspaces:\n  - !<ColorSpace>\n    name: lin\n  - !<ColorSpace>\n    name: graded\n    to_reference: !<FileTransform> {src: grade.cube, interpolation: linear}\n";
+    write(&config, text, 1_000);
+    let mut s = session(None);
+    let file = shot(&mut s, "OCIO File Transform", &[("file", json!(lut.to_string_lossy()))]);
+    let custom = shot(
+        &mut s,
+        "OCIO Color Space Transform",
+        &[("config", json!(1)), ("configFile", json!(config.to_string_lossy())), ("sourceName", json!("graded")), ("destinationName", json!("lin"))],
+    );
+    assert_all(colours(&s, file), 0.0);
+    assert_all(colours(&s, custom), 0.0);
+    // (the first key of a config's layer can't know the LUTs it names before it is read)
+    assert_all(colours(&s, custom), 0.0);
+    let misses = s.layer_cache.stats().misses;
+    assert_all(colours(&s, file), 0.0);
+    assert_all(colours(&s, custom), 0.0);
+    assert_eq!(s.layer_cache.stats().misses, misses, "unchanged files keep the cached layers");
+    let log = ReadLog::new();
+    let mut r = s.renderer(RenderOpts::default());
+    r.reads = Some(&log);
+    let _ = r.comp_frame(custom.1, Tick::ZERO);
+    let files = log.into_files();
+    assert!(files.get(&grade.to_string_lossy()).is_some(), "the render notes the config's LUT: {files:?}");
+    let generation = effectcraft_effects::lut_generation();
+    write(&lut, WHITE, 2_000);
+    assert_all(colours(&s, file), 1.0);
+    write(&grade, WHITE, 2_000);
+    assert_all(colours(&s, custom), 1.0);
+    assert!(effectcraft_effects::lut_generation() > generation, "the viewer's frames made before are dropped");
+}
diff --git a/crates/render/src/cache/dependencies.rs b/crates/render/src/cache/dependencies.rs
index 5e8a8845b..6f14ddcde 100644
--- a/crates/render/src/cache/dependencies.rs
+++ b/crates/render/src/cache/dependencies.rs
@@ -175,11 +175,8 @@ impl Dependencies<'_> {
                             // Properties overrides, which the render applies: a LUT file one of
                             // them names is read too (#3493).
                             for o in crate::fx_host::essential_overrides(ctx, layer) {
-                                if let effectcraft_keyframe::Value::Str(src) = &o.value
-                                    && let Some(path) = effectcraft_effects::lut_file(src)
-                                {
-                                    crate::reads::ReadFile::new(path, crate::reads::FileStamp::native(path).unwrap_or(crate::reads::FileStamp::Missing))
-                                        .hash(self.h);
+                                if let effectcraft_keyframe::Value::Str(src) = &o.value {
+                                    crate::reads::source_files(src).hash(self.h);
                                 }
                             }
                             let nested = EvalCtx::new(ctx.project, item, comp, time);
diff --git a/crates/render/src/reads.rs b/crates/render/src/reads.rs
index 9021f1e42..73b7ce830 100644
--- a/crates/render/src/reads.rs
+++ b/crates/render/src/reads.rs
@@ -65,20 +65,31 @@ impl ReadFile {
     }
 }
 
-/// The LUT files effect `g` of `layer` reads at the context time (Apply Color LUT, Lumetri's
-/// Input LUT and Look), each with its identity now. A layer's cache key holds them and a render
+/// The files effect `g` of `layer` reads at the context time (Apply Color LUT, Lumetri's Input
+/// LUT and Look, OCIO File Transform, a custom OCIO config and its LUTs: see
+/// [`effectcraft_effects::lut_params`]), each with its identity now. A layer's cache key holds them and a render
 /// notes them, so what was made with a file that changed since is not used (#3493).
 pub(crate) fn lut_files(ctx: &crate::EvalCtx, layer: &effectcraft_project::Layer, g: &effectcraft_project::PropGroup) -> Vec<ReadFile> {
     let effectcraft_project::GroupKind::Effect { effect } = &g.kind else { return Vec::new() };
     effectcraft_effects::lut_params(effect)
         .iter()
         .filter_map(|param| match ctx.value(layer, g.prop(param)?) {
-            effectcraft_keyframe::Value::Str(src) => {
-                let path = effectcraft_effects::lut_file(&src)?;
-                Some(ReadFile::new(path, FileStamp::native(path).unwrap_or(FileStamp::Missing)))
-            }
+            effectcraft_keyframe::Value::Str(src) => Some(source_files(&src)),
             _ => None,
         })
+        .flatten()
+        .collect()
+}
+
+/// The files a file parameter set to `src` reads (an OCIO config's also the LUTs it names, #3538),
+/// each with its identity now.
+pub(crate) fn source_files(src: &str) -> Vec<ReadFile> {
+    effectcraft_effects::lut_files(src)
+        .into_iter()
+        .map(|path| {
+            let stamp = FileStamp::native(&path).unwrap_or(FileStamp::Missing);
+            ReadFile::new(path, stamp)
+        })
         .collect()
 }