diff --git a/CHANGELOG.md b/CHANGELOG.md
index 887b9edb..874feff9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,11 @@ and this project adheres to
 
 - @cosmjs/cosmwasm-stargate: Codec adapted to support wasmd 0.16. Older versions
   of wasmd are not supported anymore.
+- @cosmjs/tendermint-rpc: The fields `CommitSignature.validatorAddress`,
+  `.timestamp` and `.signature` are now optional. They are unset when
+  `blockIdFlag` is `BlockIdFlag.Absent`. The decoding into `CommitSignature` is
+  only updated for the class `Tendermint34Client`, not for `Client`. Please
+  migrate to the former.
 
 ## [0.24.0] - 2021-03-11
 
diff --git a/packages/tendermint-rpc/src/legacy/client.spec.ts b/packages/tendermint-rpc/src/legacy/client.spec.ts
index fc1dd0b2..a3c290a5 100644
--- a/packages/tendermint-rpc/src/legacy/client.spec.ts
+++ b/packages/tendermint-rpc/src/legacy/client.spec.ts
@@ -105,9 +105,9 @@ function defaultTestSuite(rpcFactory: () => RpcClient, adaptor: Adaptor, expecte
     expect(response).toBeTruthy();
     expect(response.commit.signatures.length).toBeGreaterThanOrEqual(1);
     expect(response.commit.signatures[0].blockIdFlag).toEqual(2);
-    expect(response.commit.signatures[0].validatorAddress.length).toEqual(20);
+    expect(response.commit.signatures[0].validatorAddress?.length).toEqual(20);
     expect(response.commit.signatures[0].timestamp).toBeInstanceOf(Date);
-    expect(response.commit.signatures[0].signature.length).toEqual(64);
+    expect(response.commit.signatures[0].signature?.length).toEqual(64);
 
     client.disconnect();
   });
diff --git a/packages/tendermint-rpc/src/tendermint34/adaptors/v0-34/responses.ts b/packages/tendermint-rpc/src/tendermint34/adaptors/v0-34/responses.ts
index 42f98f3f..4a72eb8b 100644
--- a/packages/tendermint-rpc/src/tendermint34/adaptors/v0-34/responses.ts
+++ b/packages/tendermint-rpc/src/tendermint34/adaptors/v0-34/responses.ts
@@ -3,7 +3,7 @@ import { fromBase64, fromHex } from "@cosmjs/encoding";
 import { JsonRpcSuccessResponse } from "@cosmjs/json-rpc";
 import { assert } from "@cosmjs/utils";
 
-import { fromRfc3339WithNanoseconds } from "../../../dates";
+import { DateWithNanoseconds, fromRfc3339WithNanoseconds } from "../../../dates";
 import { SubscriptionEvent } from "../../../rpcclients";
 import { BlockIdFlag, CommitSignature, ValidatorPubkey } from "../../../types";
 import {
@@ -416,17 +416,23 @@ type RpcSignature = {
   readonly signature: string | null;
 };
 
+/**
+ * In some cases a timestamp is optional and set to the value 0 in Go.
+ * This can lead to strings like "0001-01-01T00:00:00Z" (see https://github.com/cosmos/cosmjs/issues/704#issuecomment-797122415).
+ * This decoder tries to clean up such encoding from the API and turn them
+ * into undefined values.
+ */
+function decodeOptionalTime(timestamp: string): DateWithNanoseconds | undefined {
+  const nonZeroTime = timestamp && !timestamp.startsWith("0001-01-01");
+  return nonZeroTime ? fromRfc3339WithNanoseconds(timestamp) : undefined;
+}
+
 function decodeCommitSignature(data: RpcSignature): CommitSignature {
-  const nonZeroTime = data.timestamp && !data.timestamp.startsWith("0001-01-01");
   return {
     blockIdFlag: decodeBlockIdFlag(data.block_id_flag),
-    // FIXME: Return an optional validatorAddress instead of an empty Uint8Array
-    // in the next breaking release.
-    validatorAddress: fromHex(data.validator_address),
-    timestamp: nonZeroTime ? fromRfc3339WithNanoseconds(data.timestamp) : undefined,
-    // FIXME: Return an optional signature instead of an empty Uint8Array
-    // in the next breaking release.
-    signature: fromBase64(data.signature || ""),
+    validatorAddress: data.validator_address ? fromHex(data.validator_address) : undefined,
+    timestamp: decodeOptionalTime(data.timestamp),
+    signature: data.signature ? fromBase64(data.signature) : undefined,
   };
 }
 
diff --git a/packages/tendermint-rpc/src/tendermint34/tendermint34client.spec.ts b/packages/tendermint-rpc/src/tendermint34/tendermint34client.spec.ts
index e43d2311..90598acc 100644
--- a/packages/tendermint-rpc/src/tendermint34/tendermint34client.spec.ts
+++ b/packages/tendermint-rpc/src/tendermint34/tendermint34client.spec.ts
@@ -104,9 +104,9 @@ function defaultTestSuite(rpcFactory: () => RpcClient, expected: ExpectedValues)
     expect(response).toBeTruthy();
     expect(response.commit.signatures.length).toBeGreaterThanOrEqual(1);
     expect(response.commit.signatures[0].blockIdFlag).toEqual(2);
-    expect(response.commit.signatures[0].validatorAddress.length).toEqual(20);
+    expect(response.commit.signatures[0].validatorAddress?.length).toEqual(20);
     expect(response.commit.signatures[0].timestamp).toBeInstanceOf(Date);
-    expect(response.commit.signatures[0].signature.length).toEqual(64);
+    expect(response.commit.signatures[0].signature?.length).toEqual(64);
 
     client.disconnect();
   });
diff --git a/packages/tendermint-rpc/src/types.ts b/packages/tendermint-rpc/src/types.ts
index d920f6d0..ae0c74b0 100644
--- a/packages/tendermint-rpc/src/types.ts
+++ b/packages/tendermint-rpc/src/types.ts
@@ -25,7 +25,7 @@ export enum BlockIdFlag {
 export interface CommitSignature {
   /** If this is BlockIdFlag.Absent, all other fields are expected to be unset */
   blockIdFlag: BlockIdFlag;
-  validatorAddress: Uint8Array;
-  timestamp?: ReadonlyDateWithNanoseconds;
-  signature: Uint8Array;
+  validatorAddress: Uint8Array | undefined;
+  timestamp: ReadonlyDateWithNanoseconds | undefined;
+  signature: Uint8Array | undefined;
 }