diff --git a/integration/optional-long/google/protobuf/timestamp.ts b/integration/optional-long/google/protobuf/timestamp.ts
new file mode 100644
index 000000000..12ab7cdda
--- /dev/null
+++ b/integration/optional-long/google/protobuf/timestamp.ts
@@ -0,0 +1,211 @@
+/* eslint-disable */
+import Long = require("long");
+import * as _m0 from "protobufjs/minimal";
+
+export const protobufPackage = "google.protobuf";
+
+/**
+ * A Timestamp represents a point in time independent of any time zone or local
+ * calendar, encoded as a count of seconds and fractions of seconds at
+ * nanosecond resolution. The count is relative to an epoch at UTC midnight on
+ * January 1, 1970, in the proleptic Gregorian calendar which extends the
+ * Gregorian calendar backwards to year one.
+ *
+ * All minutes are 60 seconds long. Leap seconds are "smeared" so that no leap
+ * second table is needed for interpretation, using a [24-hour linear
+ * smear](https://developers.google.com/time/smear).
+ *
+ * The range is from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59.999999999Z. By
+ * restricting to that range, we ensure that we can convert to and from [RFC
+ * 3339](https://www.ietf.org/rfc/rfc3339.txt) date strings.
+ *
+ * # Examples
+ *
+ * Example 1: Compute Timestamp from POSIX `time()`.
+ *
+ *     Timestamp timestamp;
+ *     timestamp.set_seconds(time(NULL));
+ *     timestamp.set_nanos(0);
+ *
+ * Example 2: Compute Timestamp from POSIX `gettimeofday()`.
+ *
+ *     struct timeval tv;
+ *     gettimeofday(&tv, NULL);
+ *
+ *     Timestamp timestamp;
+ *     timestamp.set_seconds(tv.tv_sec);
+ *     timestamp.set_nanos(tv.tv_usec * 1000);
+ *
+ * Example 3: Compute Timestamp from Win32 `GetSystemTimeAsFileTime()`.
+ *
+ *     FILETIME ft;
+ *     GetSystemTimeAsFileTime(&ft);
+ *     UINT64 ticks = (((UINT64)ft.dwHighDateTime) << 32) | ft.dwLowDateTime;
+ *
+ *     // A Windows tick is 100 nanoseconds. Windows epoch 1601-01-01T00:00:00Z
+ *     // is 11644473600 seconds before Unix epoch 1970-01-01T00:00:00Z.
+ *     Timestamp timestamp;
+ *     timestamp.set_seconds((INT64) ((ticks / 10000000) - 11644473600LL));
+ *     timestamp.set_nanos((INT32) ((ticks % 10000000) * 100));
+ *
+ * Example 4: Compute Timestamp from Java `System.currentTimeMillis()`.
+ *
+ *     long millis = System.currentTimeMillis();
+ *
+ *     Timestamp timestamp = Timestamp.newBuilder().setSeconds(millis / 1000)
+ *         .setNanos((int) ((millis % 1000) * 1000000)).build();
+ *
+ * Example 5: Compute Timestamp from Java `Instant.now()`.
+ *
+ *     Instant now = Instant.now();
+ *
+ *     Timestamp timestamp =
+ *         Timestamp.newBuilder().setSeconds(now.getEpochSecond())
+ *             .setNanos(now.getNano()).build();
+ *
+ * Example 6: Compute Timestamp from current time in Python.
+ *
+ *     timestamp = Timestamp()
+ *     timestamp.GetCurrentTime()
+ *
+ * # JSON Mapping
+ *
+ * In JSON format, the Timestamp type is encoded as a string in the
+ * [RFC 3339](https://www.ietf.org/rfc/rfc3339.txt) format. That is, the
+ * format is "{year}-{month}-{day}T{hour}:{min}:{sec}[.{frac_sec}]Z"
+ * where {year} is always expressed using four digits while {month}, {day},
+ * {hour}, {min}, and {sec} are zero-padded to two digits each. The fractional
+ * seconds, which can go up to 9 digits (i.e. up to 1 nanosecond resolution),
+ * are optional. The "Z" suffix indicates the timezone ("UTC"); the timezone
+ * is required. A proto3 JSON serializer should always use UTC (as indicated by
+ * "Z") when printing the Timestamp type and a proto3 JSON parser should be
+ * able to accept both UTC and other timezones (as indicated by an offset).
+ *
+ * For example, "2017-01-15T01:30:15.01Z" encodes 15.01 seconds past
+ * 01:30 UTC on January 15, 2017.
+ *
+ * In JavaScript, one can convert a Date object to this format using the
+ * standard
+ * [toISOString()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toISOString)
+ * method. In Python, a standard `datetime.datetime` object can be converted
+ * to this format using
+ * [`strftime`](https://docs.python.org/2/library/time.html#time.strftime) with
+ * the time format spec '%Y-%m-%dT%H:%M:%S.%fZ'. Likewise, in Java, one can use
+ * the Joda Time's [`ISODateTimeFormat.dateTime()`](
+ * http://www.joda.org/joda-time/apidocs/org/joda/time/format/ISODateTimeFormat.html#dateTime%2D%2D
+ * ) to obtain a formatter capable of generating timestamps in this format.
+ */
+export interface Timestamp {
+  /**
+   * Represents seconds of UTC time since Unix epoch
+   * 1970-01-01T00:00:00Z. Must be from 0001-01-01T00:00:00Z to
+   * 9999-12-31T23:59:59Z inclusive.
+   */
+  seconds?:
+    | Long
+    | undefined;
+  /**
+   * Non-negative fractions of a second at nanosecond resolution. Negative
+   * second values with fractions must still have non-negative nanos values
+   * that count forward in time. Must be from 0 to 999,999,999
+   * inclusive.
+   */
+  nanos?: number | undefined;
+}
+
+function createBaseTimestamp(): Timestamp {
+  return { seconds: Long.ZERO, nanos: 0 };
+}
+
+export const Timestamp = {
+  encode(message: Timestamp, writer: _m0.Writer = _m0.Writer.create()): _m0.Writer {
+    if (message.seconds !== undefined && !message.seconds.isZero()) {
+      writer.uint32(8).int64(message.seconds);
+    }
+    if (message.nanos !== undefined && message.nanos !== 0) {
+      writer.uint32(16).int32(message.nanos);
+    }
+    return writer;
+  },
+
+  decode(input: _m0.Reader | Uint8Array, length?: number): Timestamp {
+    const reader = input instanceof _m0.Reader ? input : _m0.Reader.create(input);
+    let end = length === undefined ? reader.len : reader.pos + length;
+    const message = createBaseTimestamp();
+    while (reader.pos < end) {
+      const tag = reader.uint32();
+      switch (tag >>> 3) {
+        case 1:
+          if (tag !== 8) {
+            break;
+          }
+
+          message.seconds = reader.int64() as Long;
+          continue;
+        case 2:
+          if (tag !== 16) {
+            break;
+          }
+
+          message.nanos = reader.int32();
+          continue;
+      }
+      if ((tag & 7) === 4 || tag === 0) {
+        break;
+      }
+      reader.skipType(tag & 7);
+    }
+    return message;
+  },
+
+  fromJSON(object: any): Timestamp {
+    return {
+      seconds: isSet(object.seconds) ? Long.fromValue(object.seconds) : Long.ZERO,
+      nanos: isSet(object.nanos) ? globalThis.Number(object.nanos) : 0,
+    };
+  },
+
+  toJSON(message: Timestamp): unknown {
+    const obj: any = {};
+    if (message.seconds !== undefined && !message.seconds.isZero()) {
+      obj.seconds = (message.seconds || Long.ZERO).toString();
+    }
+    if (message.nanos !== undefined && message.nanos !== 0) {
+      obj.nanos = Math.round(message.nanos);
+    }
+    return obj;
+  },
+
+  create<I extends Exact<DeepPartial<Timestamp>, I>>(base?: I): Timestamp {
+    return Timestamp.fromPartial(base ?? ({} as any));
+  },
+  fromPartial<I extends Exact<DeepPartial<Timestamp>, I>>(object: I): Timestamp {
+    const message = createBaseTimestamp();
+    message.seconds = (object.seconds !== undefined && object.seconds !== null)
+      ? Long.fromValue(object.seconds)
+      : Long.ZERO;
+    message.nanos = object.nanos ?? 0;
+    return message;
+  },
+};
+
+type Builtin = Date | Function | Uint8Array | string | number | boolean | undefined;
+
+export type DeepPartial<T> = T extends Builtin ? T
+  : T extends Long ? string | number | Long : T extends globalThis.Array<infer U> ? globalThis.Array<DeepPartial<U>>
+  : T extends ReadonlyArray<infer U> ? ReadonlyArray<DeepPartial<U>>
+  : T extends {} ? { [K in keyof T]?: DeepPartial<T[K]> }
+  : Partial<T>;
+
+type KeysOfUnion<T> = T extends T ? keyof T : never;
+export type Exact<P, I extends P> = P extends Builtin ? P
+  : P & { [K in keyof P]: Exact<P[K], I[K]> } & { [K in Exclude<keyof I, KeysOfUnion<P>>]: never };
+
+if (_m0.util.Long !== Long) {
+  _m0.util.Long = Long as any;
+  _m0.configure();
+}
+
+function isSet(value: any): boolean {
+  return value !== null && value !== undefined;
+}
diff --git a/integration/optional-long/parameters.txt b/integration/optional-long/parameters.txt
new file mode 100644
index 000000000..f2edb471a
--- /dev/null
+++ b/integration/optional-long/parameters.txt
@@ -0,0 +1 @@
+useOptionals=all,forceLong=long
diff --git a/integration/optional-long/test.bin b/integration/optional-long/test.bin
new file mode 100644
index 000000000..982bd337e
Binary files /dev/null and b/integration/optional-long/test.bin differ
diff --git a/integration/optional-long/test.proto b/integration/optional-long/test.proto
new file mode 100644
index 000000000..a40710e22
--- /dev/null
+++ b/integration/optional-long/test.proto
@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+import "google/protobuf/timestamp.proto";
+
+message Example {
+  google.protobuf.Timestamp datetime = 1;
+}
diff --git a/integration/optional-long/test.ts b/integration/optional-long/test.ts
new file mode 100644
index 000000000..8dc400d03
--- /dev/null
+++ b/integration/optional-long/test.ts
@@ -0,0 +1,114 @@
+/* eslint-disable */
+import * as _m0 from "protobufjs/minimal";
+import { Timestamp } from "./google/protobuf/timestamp";
+import Long = require("long");
+
+export const protobufPackage = "";
+
+export interface Example {
+  datetime?: Date | undefined;
+}
+
+function createBaseExample(): Example {
+  return { datetime: undefined };
+}
+
+export const Example = {
+  encode(message: Example, writer: _m0.Writer = _m0.Writer.create()): _m0.Writer {
+    if (message.datetime !== undefined) {
+      Timestamp.encode(toTimestamp(message.datetime), writer.uint32(10).fork()).ldelim();
+    }
+    return writer;
+  },
+
+  decode(input: _m0.Reader | Uint8Array, length?: number): Example {
+    const reader = input instanceof _m0.Reader ? input : _m0.Reader.create(input);
+    let end = length === undefined ? reader.len : reader.pos + length;
+    const message = createBaseExample();
+    while (reader.pos < end) {
+      const tag = reader.uint32();
+      switch (tag >>> 3) {
+        case 1:
+          if (tag !== 10) {
+            break;
+          }
+
+          message.datetime = fromTimestamp(Timestamp.decode(reader, reader.uint32()));
+          continue;
+      }
+      if ((tag & 7) === 4 || tag === 0) {
+        break;
+      }
+      reader.skipType(tag & 7);
+    }
+    return message;
+  },
+
+  fromJSON(object: any): Example {
+    return { datetime: isSet(object.datetime) ? fromJsonTimestamp(object.datetime) : undefined };
+  },
+
+  toJSON(message: Example): unknown {
+    const obj: any = {};
+    if (message.datetime !== undefined) {
+      obj.datetime = message.datetime.toISOString();
+    }
+    return obj;
+  },
+
+  create<I extends Exact<DeepPartial<Example>, I>>(base?: I): Example {
+    return Example.fromPartial(base ?? ({} as any));
+  },
+  fromPartial<I extends Exact<DeepPartial<Example>, I>>(object: I): Example {
+    const message = createBaseExample();
+    message.datetime = object.datetime ?? undefined;
+    return message;
+  },
+};
+
+type Builtin = Date | Function | Uint8Array | string | number | boolean | undefined;
+
+export type DeepPartial<T> = T extends Builtin ? T
+  : T extends Long ? string | number | Long : T extends globalThis.Array<infer U> ? globalThis.Array<DeepPartial<U>>
+  : T extends ReadonlyArray<infer U> ? ReadonlyArray<DeepPartial<U>>
+  : T extends {} ? { [K in keyof T]?: DeepPartial<T[K]> }
+  : Partial<T>;
+
+type KeysOfUnion<T> = T extends T ? keyof T : never;
+export type Exact<P, I extends P> = P extends Builtin ? P
+  : P & { [K in keyof P]: Exact<P[K], I[K]> } & { [K in Exclude<keyof I, KeysOfUnion<P>>]: never };
+
+function toTimestamp(date: Date): Timestamp {
+  const seconds = numberToLong(date.getTime() / 1_000);
+  const nanos = (date.getTime() % 1_000) * 1_000_000;
+  return { seconds, nanos };
+}
+
+function fromTimestamp(t: Timestamp): Date {
+  let millis = (t.seconds?.toNumber() || 0) * 1_000;
+  millis += (t.nanos || 0) / 1_000_000;
+  return new globalThis.Date(millis);
+}
+
+function fromJsonTimestamp(o: any): Date {
+  if (o instanceof globalThis.Date) {
+    return o;
+  } else if (typeof o === "string") {
+    return new globalThis.Date(o);
+  } else {
+    return fromTimestamp(Timestamp.fromJSON(o));
+  }
+}
+
+function numberToLong(number: number) {
+  return Long.fromNumber(number);
+}
+
+if (_m0.util.Long !== Long) {
+  _m0.util.Long = Long as any;
+  _m0.configure();
+}
+
+function isSet(value: any): boolean {
+  return value !== null && value !== undefined;
+}
diff --git a/src/main.ts b/src/main.ts
index 51770f48a..e242e44fa 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -672,11 +672,14 @@ function makeTimestampMethods(
 
   let seconds: string | Code = "date.getTime() / 1_000";
   let toNumberCode: string | Code = "t.seconds";
+  const makeToNumberCode = (methodCall: string) =>
+    `t.seconds${options.useOptionals === "all" ? "?" : ""}.${methodCall}`;
+
   if (options.forceLong === LongOption.LONG) {
-    toNumberCode = "t.seconds.toNumber()";
+    toNumberCode = makeToNumberCode("toNumber()");
     seconds = code`${longs.numberToLong}(date.getTime() / 1_000)`;
   } else if (options.forceLong === LongOption.BIGINT) {
-    toNumberCode = code`${bytes.globalThis}.Number(t.seconds.toString())`;
+    toNumberCode = code`${bytes.globalThis}.Number(${makeToNumberCode("toString()")})`;
     seconds = code`BigInt(Math.trunc(date.getTime() / 1_000))`;
   } else if (options.forceLong === LongOption.STRING) {
     toNumberCode = code`${bytes.globalThis}.Number(t.seconds)`;