diff --git a/dist/src/crdt-automerge.js b/dist/src/crdt-automerge.js
index 57557a9..51fa578 100644
--- a/dist/src/crdt-automerge.js
+++ b/dist/src/crdt-automerge.js
@@ -65,7 +65,7 @@ export const encodeAutomergeFieldWrite = (value, type) => {
     if (isAutomergeFieldDoc(value)) {
         return saveAutomergeFieldDoc(value, type);
     }
-    return createAutomergeFieldValue(value, type);
+    throw new Error("CRDT field writes must use an Automerge document or Camino CRDT envelope");
 };
 export const normalizeAutomergeFieldValue = (value, type) => encodeAutomergeFieldWrite(value, type);
 export const materializeAutomergeFieldValue = (value, type) => loadAutomergeFieldDoc(value, type).value;
@@ -80,4 +80,4 @@ export const mergeAutomergeFieldValues = ({ existing, incoming, type, }) => {
         materialized: mergedDoc.value,
     };
 };
-//# sourceMappingURL=crdt-automerge.js.map
\ No newline at end of file
+//# sourceMappingURL=crdt-automerge.js.map
diff --git a/src/crdt-automerge.ts b/src/crdt-automerge.ts
index 00ca01b..d89071d 100644
--- a/src/crdt-automerge.ts
+++ b/src/crdt-automerge.ts
@@ -111,7 +111,9 @@ export const encodeAutomergeFieldWrite = (
   if (isAutomergeFieldDoc(value)) {
     return saveAutomergeFieldDoc(value, type);
   }
-  return createAutomergeFieldValue(value, type);
+  throw new Error(
+    "CRDT field writes must use an Automerge document or Camino CRDT envelope",
+  );
 };
 
 export const normalizeAutomergeFieldValue = (
diff --git a/test/crdt-automerge.test.ts b/test/crdt-automerge.test.ts
index 43bc4dc..95cfc0c 100644
--- a/test/crdt-automerge.test.ts
+++ b/test/crdt-automerge.test.ts
@@ -13,7 +13,7 @@ import {
 
 const type = "camino.CrdtJson";
 
-test("Automerge CRDT fields lift plain values into stored envelopes", () => {
+test("Automerge CRDT fields explicitly create stored envelopes", () => {
   const stored = createAutomergeFieldValue({ title: "draft" }, type);
 
   assert.equal(stored.$caminoCrdtType, type);
@@ -23,6 +23,13 @@ test("Automerge CRDT fields lift plain values into stored envelopes", () => {
   });
 });
 
+test("Automerge CRDT field writes reject plain values", () => {
+  assert.throws(
+    () => encodeAutomergeFieldWrite({ title: "draft" }, type),
+    /CRDT field writes must use an Automerge document/,
+  );
+});
+
 test("Automerge CRDT fields encode rehydrated docs for writes", () => {
   const base = loadAutomergeFieldDoc(
     createAutomergeFieldValue({ title: "draft" }, type),