diff --git a/packages/compiler/test/ts7/baselines/order-parity/tests/corpus/5913-prototype-type-error-messages.ts.json b/packages/compiler/test/ts7/baselines/order-parity/tests/corpus/5913-prototype-type-error-messages.ts.json
new file mode 100644
index 000000000..f7e3d10b9
--- /dev/null
+++ b/packages/compiler/test/ts7/baselines/order-parity/tests/corpus/5913-prototype-type-error-messages.ts.json
@@ -0,0 +1,6 @@
+{
+ "order": [
+  "<repo>/tests/corpus/5913-prototype-type-error-messages.ts"
+ ],
+ "diags": []
+}
diff --git a/packages/runtime/src/scr_json.c b/packages/runtime/src/scr_json.c
index cdfb3d0f9..958112b66 100644
--- a/packages/runtime/src/scr_json.c
+++ b/packages/runtime/src/scr_json.c
@@ -1729,13 +1729,40 @@ static bool scr_dyn_typed_ref_prototype(const ScrDyn *value) {
   return view && (view->kind == SCR_DYN_OBJ || view->kind == SCR_DYN_ARR);
 }
 
+/* True when `prototype` is null or an object or function, the values
+ * Object.create and Object.setPrototypeOf accept. Otherwise throws Node's
+ * TypeError, whose message ends with the value's string form. */
+static bool scr_dyn_prototype_valid(const ScrDyn *prototype) {
+  if (scr_dyn_is_object(prototype) || scr_dyn_is_callable(prototype)) return true;
+  if (scr_exc_pending()) return false;
+  ScrStr *text = prototype->kind == SCR_DYN_SYMBOL
+    ? prototype->v.symbol.render(prototype->v.symbol.value) : scr_dyn_string_coerce_js(prototype);
+  if (!text) return false;
+  ScrJsonBuf b;
+  scr_jb_init(&b);
+  scr_jb_puts(&b, "Object prototype may only be an Object or null: ");
+  scr_jb_put_str(&b, text);
+  scr_str_release(text);
+  scr_throw_error(SCR_ERR_TYPE, scr_jb_finish(&b));
+  return false;
+}
+
+/* A valid receiver or prototype whose kind this operation does not handle. */
+static void scr_dyn_prototype_unsupported(const char *operation) {
+  ScrJsonBuf b;
+  scr_jb_init(&b);
+  scr_jb_puts(&b, operation);
+  scr_jb_puts(&b, " with this value is not supported yet");
+  scr_throw_error(SCR_ERR_ERROR, scr_jb_finish(&b));
+}
+
 ScrDyn *scr_dyn_obj_create(ScrDyn *prototype) {
+  if (!scr_dyn_prototype_valid(prototype)) return NULL;
   if (prototype != scr_builtin_object_prototype && scr_dyn_class_reflection_fence(prototype)) return NULL;
   bool typed = scr_dyn_typed_ref_prototype(prototype);
   if (scr_exc_pending()) return NULL;
   if (prototype->kind != SCR_DYN_OBJ && prototype->kind != SCR_DYN_ARR && prototype->kind != SCR_DYN_NULL && !typed) {
-    static const char message[] = "Object prototype may only be an Object or null";
-    scr_throw_error_msg(SCR_ERR_TYPE, message, sizeof message - 1);
+    scr_dyn_prototype_unsupported("Object.create");
     return NULL;
   }
   ScrDyn *object = prototype->kind == SCR_DYN_NULL ? scr_dyn_new_obj_null_proto() : scr_dyn_new_obj();
@@ -1786,12 +1813,7 @@ ScrDyn *scr_dyn_set_prototype(ScrDyn *object, ScrDyn *prototype) {
    * only check. */
   if (object->kind == SCR_DYN_BOOL || object->kind == SCR_DYN_NUM || object->kind == SCR_DYN_STR ||
       object->kind == SCR_DYN_BIGINT || object->kind == SCR_DYN_SYMBOL) {
-    bool valid = scr_dyn_is_object(prototype) || scr_dyn_is_callable(prototype);
-    if (scr_exc_pending()) return NULL;
-    if (valid) return scr_dyn_retain(object);
-    static const char message[] = "Object prototype may only be an Object or null";
-    scr_throw_error_msg(SCR_ERR_TYPE, message, sizeof message - 1);
-    return NULL;
+    return scr_dyn_prototype_valid(prototype) ? scr_dyn_retain(object) : NULL;
   }
   if (scr_dyn_class_reflection_fence(object) || scr_dyn_class_reflection_fence(prototype)) return NULL;
   if (object->kind == SCR_DYN_TYPED_REF) {
@@ -1821,12 +1843,12 @@ ScrDyn *scr_dyn_set_prototype(ScrDyn *object, ScrDyn *prototype) {
     scr_throw_error_msg(SCR_ERR_TYPE, message, sizeof message - 1);
     return NULL;
   }
+  if (!scr_dyn_prototype_valid(prototype)) return NULL;
   bool typed = scr_dyn_typed_ref_prototype(prototype);
   if (scr_exc_pending()) return NULL;
   if ((object->kind != SCR_DYN_OBJ && object->kind != SCR_DYN_ARR) ||
       (prototype->kind != SCR_DYN_OBJ && prototype->kind != SCR_DYN_ARR && prototype->kind != SCR_DYN_FUNC && prototype->kind != SCR_DYN_NULL && !typed)) {
-    static const char message[] = "Object prototype may only be an Object or null";
-    scr_throw_error_msg(SCR_ERR_TYPE, message, sizeof message - 1);
+    scr_dyn_prototype_unsupported("Object.setPrototypeOf");
     return NULL;
   }
   for (const ScrDyn *current = scr_dyn_chain_link(prototype); current;) {
diff --git a/tests/corpus/5913-prototype-type-error-messages.ts b/tests/corpus/5913-prototype-type-error-messages.ts
new file mode 100644
index 000000000..cb78e4cb1
--- /dev/null
+++ b/tests/corpus/5913-prototype-type-error-messages.ts
@@ -0,0 +1,39 @@
+// Object.setPrototypeOf and Object.create reject a prototype that is
+// neither an object nor null with Node's TypeError, whose message ends with
+// the value's string form: numbers as String(n) (-0 as 0), bigints without
+// the n suffix, symbols as Symbol(description), and the empty string as
+// nothing.
+
+function message(run: () => unknown): string {
+  try {
+    run();
+    return "no error";
+  } catch (error) {
+    return `${error instanceof TypeError} ${(error as Error).message}`;
+  }
+}
+
+const prototypes: [string, unknown][] = [
+  ["number", 7],
+  ["fraction", 1.5],
+  ["negative zero", -0],
+  ["nan", NaN],
+  ["string", "proto"],
+  ["empty string", ""],
+  ["boolean", true],
+  ["undefined", undefined],
+  ["bigint", 10n],
+  ["symbol", Symbol("tag")],
+];
+
+for (const [label, prototype] of prototypes) {
+  const invalid = prototype as object | null;
+  const target: unknown = JSON.parse('{"own":1}');
+  console.log(label, "object receiver |", message(() => Object.setPrototypeOf(target, invalid)));
+  console.log(label, "primitive receiver |", message(() => Object.setPrototypeOf(5, invalid)));
+  console.log(label, "create |", message(() => Object.create(invalid)));
+}
+
+const valid: unknown = JSON.parse('{"own":1}');
+console.log("null prototype |", message(() => Object.setPrototypeOf(valid, null)));
+console.log("object prototype |", message(() => Object.create({ inherited: true })));
diff --git a/tests/harness/corpus-costs.json b/tests/harness/corpus-costs.json
index 8f6ba50bb..8877c5042 100644
--- a/tests/harness/corpus-costs.json
+++ b/tests/harness/corpus-costs.json
@@ -1841,6 +1841,9 @@
     "5648-dns-lookup-forms.ts": 2992,
     "5649-dns-service-servers.ts": 2712,
     "5650-dns-lookup-errors-untyped.cjs": 2822,
+    "5910-set-prototype-of-primitive-object-kinds.ts": 2719,
+    "5911-dyn-class-to-primitive.ts": 2850,
+    "5913-prototype-type-error-messages.ts": 2484,
     "5939-js-let-object-reassigned-wider.js": 1945,
     "5950-tuple-predicate-methods.ts": 5990,
     "5951-result-never-widening.ts": 4710,
@@ -4473,6 +4476,9 @@
     "5648-dns-lookup-forms.ts": 3416,
     "5649-dns-service-servers.ts": 4916,
     "5650-dns-lookup-errors-untyped.cjs": 3889,
+    "5910-set-prototype-of-primitive-object-kinds.ts": 5033,
+    "5911-dyn-class-to-primitive.ts": 4732,
+    "5913-prototype-type-error-messages.ts": 4068,
     "5939-js-let-object-reassigned-wider.js": 4436,
     "5950-tuple-predicate-methods.ts": 7790,
     "5951-result-never-widening.ts": 6120,