diff --git a/integration/generic-metadata/hero.ts b/integration/generic-metadata/hero.ts
index 80923a5c1..d8fab5941 100644
--- a/integration/generic-metadata/hero.ts
+++ b/integration/generic-metadata/hero.ts
@@ -290,7 +290,7 @@ export const HeroServiceDefinition = {
       requestStream: false,
       responseType: Hero,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     findOneVillain: {
       name: "FindOneVillain",
@@ -298,7 +298,7 @@ export const HeroServiceDefinition = {
       requestStream: false,
       responseType: Villain,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     findManyVillain: {
       name: "FindManyVillain",
@@ -306,7 +306,7 @@ export const HeroServiceDefinition = {
       requestStream: true,
       responseType: Villain,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
   },
 } as const;
diff --git a/integration/generic-service-definitions-and-services/simple.ts b/integration/generic-service-definitions-and-services/simple.ts
index d1c322674..de1c63b67 100644
--- a/integration/generic-service-definitions-and-services/simple.ts
+++ b/integration/generic-service-definitions-and-services/simple.ts
@@ -70,7 +70,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     serverStreaming: {
       name: "ServerStreaming",
@@ -78,7 +78,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
     clientStreaming: {
       name: "ClientStreaming",
@@ -86,7 +86,7 @@ export const TestDefinition = {
       requestStream: true,
       responseType: TestMessage,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     bidiStreaming: {
       name: "BidiStreaming",
@@ -94,7 +94,7 @@ export const TestDefinition = {
       requestStream: true,
       responseType: TestMessage,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
     /** @deprecated */
     deprecated: {
@@ -103,7 +103,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     idempotent: {
       name: "Idempotent",
@@ -111,7 +111,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: false,
-      options: { idempotencyLevel: "IDEMPOTENT" },
+      options: { idempotencyLevel: "IDEMPOTENT", _unknownFields: {} },
     },
     noSideEffects: {
       name: "NoSideEffects",
@@ -119,7 +119,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: false,
-      options: { idempotencyLevel: "NO_SIDE_EFFECTS" },
+      options: { idempotencyLevel: "NO_SIDE_EFFECTS", _unknownFields: {} },
     },
   },
 } as const;
diff --git a/integration/generic-service-definitions/simple.ts b/integration/generic-service-definitions/simple.ts
index d1c322674..de1c63b67 100644
--- a/integration/generic-service-definitions/simple.ts
+++ b/integration/generic-service-definitions/simple.ts
@@ -70,7 +70,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     serverStreaming: {
       name: "ServerStreaming",
@@ -78,7 +78,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
     clientStreaming: {
       name: "ClientStreaming",
@@ -86,7 +86,7 @@ export const TestDefinition = {
       requestStream: true,
       responseType: TestMessage,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     bidiStreaming: {
       name: "BidiStreaming",
@@ -94,7 +94,7 @@ export const TestDefinition = {
       requestStream: true,
       responseType: TestMessage,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
     /** @deprecated */
     deprecated: {
@@ -103,7 +103,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     idempotent: {
       name: "Idempotent",
@@ -111,7 +111,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: false,
-      options: { idempotencyLevel: "IDEMPOTENT" },
+      options: { idempotencyLevel: "IDEMPOTENT", _unknownFields: {} },
     },
     noSideEffects: {
       name: "NoSideEffects",
@@ -119,7 +119,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: false,
-      options: { idempotencyLevel: "NO_SIDE_EFFECTS" },
+      options: { idempotencyLevel: "NO_SIDE_EFFECTS", _unknownFields: {} },
     },
   },
 } as const;
diff --git a/integration/nice-grpc/simple.ts b/integration/nice-grpc/simple.ts
index a9fb0873c..73ff2028a 100644
--- a/integration/nice-grpc/simple.ts
+++ b/integration/nice-grpc/simple.ts
@@ -94,7 +94,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: Empty,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     unaryStringValue: {
       name: "UnaryStringValue",
@@ -207,7 +207,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: TestMessage,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
     serverStreamingStringValue: {
       name: "ServerStreamingStringValue",
@@ -215,7 +215,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: StringValue,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
     serverStreamingStruct: {
       name: "ServerStreamingStruct",
@@ -223,7 +223,7 @@ export const TestDefinition = {
       requestStream: false,
       responseType: Struct,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
     /** Client Streaming */
     clientStreaming: {
@@ -232,7 +232,7 @@ export const TestDefinition = {
       requestStream: true,
       responseType: TestMessage,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     clientStreamingStringValue: {
       name: "ClientStreamingStringValue",
@@ -240,7 +240,7 @@ export const TestDefinition = {
       requestStream: true,
       responseType: StringValue,
       responseStream: false,
-      options: {},
+      options: { _unknownFields: {} },
     },
     /** Bidi Streaming */
     bidiStreaming: {
@@ -249,7 +249,7 @@ export const TestDefinition = {
       requestStream: true,
       responseType: TestMessage,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
     bidiStreamingStringValue: {
       name: "BidiStreamingStringValue",
@@ -257,7 +257,7 @@ export const TestDefinition = {
       requestStream: true,
       responseType: StringValue,
       responseStream: true,
-      options: {},
+      options: { _unknownFields: {} },
     },
   },
 } as const;
diff --git a/src/generate-generic-service-definition.ts b/src/generate-generic-service-definition.ts
index 0ba118d1b..963fd9d9e 100644
--- a/src/generate-generic-service-definition.ts
+++ b/src/generate-generic-service-definition.ts
@@ -71,12 +71,12 @@ function generateMethodDefinition(ctx: Context, methodDesc: MethodDescriptorProt
       requestStream: ${methodDesc.clientStreaming},
       responseType: ${outputType},
       responseStream: ${methodDesc.serverStreaming},
-      options: ${generateMethodOptions(methodDesc.options)}
+      options: ${generateMethodOptions(ctx, methodDesc.options)}
     }
   `;
 }
 
-function generateMethodOptions(options: MethodOptions | undefined) {
+function generateMethodOptions(ctx: Context, options: MethodOptions | undefined) {
   const chunks: Code[] = [];
 
   chunks.push(code`{`);
@@ -87,6 +87,29 @@ function generateMethodOptions(options: MethodOptions | undefined) {
     } else if (options.idempotencyLevel === MethodOptions_IdempotencyLevel.NO_SIDE_EFFECTS) {
       chunks.push(code`idempotencyLevel: 'NO_SIDE_EFFECTS',`);
     }
+
+    if ("_unknownFields" in options) {
+      const msgUnknownFields: any = (options as any)["_unknownFields"];
+      const unknownFieldsChunks: Code[] = [];
+
+      unknownFieldsChunks.push(code`{`);
+
+      for (const key of Object.keys(msgUnknownFields)) {
+        const values = msgUnknownFields[key] as Uint8Array[];
+        const valuesChunks: Code[] = [];
+
+        for (const value of values) {
+          valuesChunks.push(
+            code`${ctx.options.env == "node" ? "Buffer.from" : "new Uint8Array"}([${value.join(", ")}])`
+          );
+        }
+
+        unknownFieldsChunks.push(code`${key}: [\n${joinCode(valuesChunks, { on: "," }).toCodeString([])}\n],`);
+      }
+
+      unknownFieldsChunks.push(code`}`);
+      chunks.push(code`_unknownFields: ${joinCode(unknownFieldsChunks, { on: "\n" }).toCodeString([])}`);
+    }
   }
 
   chunks.push(code`}`);