diff --git a/packages/compiler/test/ts7/baselines/order-parity/tests/corpus/5633-zlib-typed-options.ts.json b/packages/compiler/test/ts7/baselines/order-parity/tests/corpus/5633-zlib-typed-options.ts.json
new file mode 100644
index 000000000..f4d9673d5
--- /dev/null
+++ b/packages/compiler/test/ts7/baselines/order-parity/tests/corpus/5633-zlib-typed-options.ts.json
@@ -0,0 +1,6 @@
+{
+ "order": [
+  "<repo>/tests/corpus/5633-zlib-typed-options.ts"
+ ],
+ "diags": []
+}
diff --git a/packages/runtime/src/scr_zlib.c b/packages/runtime/src/scr_zlib.c
index b61cdc1cb..ff09e7ea1 100644
--- a/packages/runtime/src/scr_zlib.c
+++ b/packages/runtime/src/scr_zlib.c
@@ -420,7 +420,22 @@ void scr_zlib_options_drop(ScrZlibOptions *o) {
   o->dict = NULL;
 }
 
+static bool scr_zlib_options_parse_object(int mode, const ScrDyn *opts, ScrZlibOptions *out);
+
+/* A typed options object (a record that crossed into a checked-dynamic
+ * slot by reference) is read through its materialized view, as a plain
+ * object is. */
 bool scr_zlib_options_parse(int mode, const ScrDyn *opts, ScrZlibOptions *out) {
+  if (opts == NULL || opts->kind != SCR_DYN_TYPED_REF) return scr_zlib_options_parse_object(mode, opts, out);
+  ScrDyn *view = scr_dyn_typed_ref_materialize(opts);
+  bool ok = false;
+  if (scr_exc_pending()) memset(out, 0, sizeof *out);
+  else ok = scr_zlib_options_parse_object(mode, view, out);
+  scr_dyn_release(view);
+  return ok;
+}
+
+static bool scr_zlib_options_parse_object(int mode, const ScrDyn *opts, ScrZlibOptions *out) {
   memset(out, 0, sizeof *out);
   out->window_bits = 15;
   out->level = Z_DEFAULT_COMPRESSION;
diff --git a/packages/runtime/src/scr_zlib_stream.c b/packages/runtime/src/scr_zlib_stream.c
index 14d8747e8..4ed717d53 100644
--- a/packages/runtime/src/scr_zlib_stream.c
+++ b/packages/runtime/src/scr_zlib_stream.c
@@ -431,6 +431,13 @@ static const char *scr_zs_class_name(int mode) {
 }
 
 ScrStream *scr_zlib_stream_new(double mode_d, ScrDyn *opts) {
+  /* A typed options object is read through its materialized view. */
+  if (opts != NULL && opts->kind == SCR_DYN_TYPED_REF) {
+    ScrDyn *view = scr_dyn_typed_ref_materialize(opts);
+    ScrStream *stream = scr_exc_pending() ? NULL : scr_zlib_stream_new(mode_d, view);
+    scr_dyn_release(view);
+    return stream;
+  }
   int mode = (int)mode_d;
   const ScrDyn *o = opts != NULL && scr_dyn_truthy(opts) ? opts : NULL;
   ScrZlibOptions zo;
diff --git a/tests/corpus/5633-zlib-typed-options.ts b/tests/corpus/5633-zlib-typed-options.ts
new file mode 100644
index 000000000..da657ca14
--- /dev/null
+++ b/tests/corpus/5633-zlib-typed-options.ts
@@ -0,0 +1,58 @@
+// zlib options held in a typed object (a cast object literal that crosses
+// into the options slot by reference) are read like a plain options
+// object: levels, windowBits and strategies apply, and out-of-range values
+// throw Node's ERR_OUT_OF_RANGE from the sync, callback, promisified and
+// stream forms.
+import * as zlib from "node:zlib";
+import { promisify } from "node:util";
+
+const data = Buffer.from("hello hello hello hello hello");
+const stored = { level: 0 } as zlib.ZlibOptions;
+const fast = { level: 1 } as zlib.ZlibOptions;
+const huffman = { strategy: zlib.constants.Z_HUFFMAN_ONLY } as zlib.ZlibOptions;
+const smallWindow = { windowBits: 9, memLevel: 1 } as zlib.ZlibOptions;
+const badLevel = { level: 99 } as zlib.ZlibOptions;
+const badWindow = { windowBits: 3 } as zlib.ZlibOptions;
+
+function attempt(label: string, run: () => void): void {
+  try {
+    run();
+    console.log(label, "ok");
+  } catch (e) {
+    const err = e as NodeJS.ErrnoException;
+    console.log(label, err.name, err.code, err.message);
+  }
+}
+
+console.log("sync stored", zlib.deflateSync(data, stored).toString("hex"));
+console.log("sync fast", zlib.deflateSync(data, fast).toString("hex"));
+console.log("sync huffman", zlib.deflateSync(data, huffman).toString("hex"));
+console.log("raw small window", zlib.deflateRawSync(data, smallWindow).toString("hex"));
+console.log("gzip stored", zlib.gzipSync(data, stored).subarray(10).toString("hex"));
+attempt("sync bad level", () => zlib.deflateSync(data, badLevel));
+attempt("sync bad window", () => zlib.inflateSync(zlib.deflateSync(data), badWindow));
+attempt("callback bad level", () => zlib.gzip(data, badLevel, () => console.log("not called")));
+attempt("stream bad level", () => zlib.createDeflate(badLevel));
+
+const deflateAsync = promisify(zlib.deflate);
+
+async function main(): Promise<void> {
+  const viaCallback = await new Promise<Buffer>((resolve, reject) =>
+    zlib.deflate(data, stored, (err, out) => (err ? reject(err) : resolve(out))),
+  );
+  console.log("callback stored", viaCallback.toString("hex"));
+  console.log("promise stored", (await deflateAsync(data, stored)).toString("hex"));
+  try {
+    await deflateAsync(data, badLevel);
+    console.log("promise bad level fulfilled");
+  } catch (e) {
+    console.log("promise bad level", (e as NodeJS.ErrnoException).code);
+  }
+  const stream = zlib.createDeflate(fast);
+  const parts: Buffer[] = [];
+  stream.on("data", (chunk: Buffer) => parts.push(chunk));
+  stream.on("end", () => console.log("stream fast", Buffer.concat(parts).toString("hex")));
+  stream.end(data);
+}
+
+main().catch((e) => console.log("unexpected", String(e)));
diff --git a/tests/harness/corpus-costs.json b/tests/harness/corpus-costs.json
index 810e6a798..e211a263b 100644
--- a/tests/harness/corpus-costs.json
+++ b/tests/harness/corpus-costs.json
@@ -1976,6 +1976,7 @@
     "5630-promisify-zlib.ts": 2503,
     "5631-promisify-crypto.ts": 2200,
     "5632-promisify-dns.ts": 1700,
+    "5633-zlib-typed-options.ts": 1800,
     "5644-net-socket-addresses.ts": 2220,
     "5645-net-socket-callbacks.ts": 2442,
     "5646-net-server-connections.ts": 2389,
@@ -5012,6 +5013,7 @@
     "5630-promisify-zlib.ts": 3392,
     "5631-promisify-crypto.ts": 2600,
     "5632-promisify-dns.ts": 2000,
+    "5633-zlib-typed-options.ts": 2200,
     "5644-net-socket-addresses.ts": 2393,
     "5645-net-socket-callbacks.ts": 2060,
     "5646-net-server-connections.ts": 2755,