diff --git a/CHANGELOG.md b/CHANGELOG.md
index 05f2b382..a371a714 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,8 +10,10 @@ and this project adheres to
 
 - @cosmjs/stargate: Fix valid values of `BondStatusString` for `validators`
   query ([#1170]).
+- @cosmjs/tendermint-rpc: Fix decoding validator updates due to slashing ([#1177]).
 
 [#1170]: https://github.com/cosmos/cosmjs/issues/1170
+[#1177]: https://github.com/cosmos/cosmjs/issues/1177
 
 ### Changed
 
diff --git a/packages/tendermint-rpc/src/tendermint34/adaptor/responses.spec.ts b/packages/tendermint-rpc/src/tendermint34/adaptor/responses.spec.ts
index 04bdd6ee..2999791d 100644
--- a/packages/tendermint-rpc/src/tendermint34/adaptor/responses.spec.ts
+++ b/packages/tendermint-rpc/src/tendermint34/adaptor/responses.spec.ts
@@ -49,6 +49,26 @@ describe("Adaptor Responses", () => {
         votingPower: 11418237,
       });
     });
+
+    it("works for block results format without voting power", () => {
+      // from https://rpc.cosmos.network/block_results?height=10883046
+      const update = decodeValidatorUpdate({
+        pub_key: {
+          Sum: {
+            type: "tendermint.crypto.PublicKey_Ed25519",
+            value: {
+              ed25519: "HjSC7VkhKih6xMhudlqfaFE8ZZnP8RKJPv4iqR7RhcE="
+            }
+          }
+        }
+      });
+      expect(update).toEqual({
+        pubkey: {
+          algorithm: "ed25519",
+          data: fromBase64("HjSC7VkhKih6xMhudlqfaFE8ZZnP8RKJPv4iqR7RhcE="),
+        },
+      });
+    });
   });
 
   describe("decodeValidatorInfo", () => {
diff --git a/packages/tendermint-rpc/src/tendermint34/adaptor/responses.ts b/packages/tendermint-rpc/src/tendermint34/adaptor/responses.ts
index d76fbce2..9413696a 100644
--- a/packages/tendermint-rpc/src/tendermint34/adaptor/responses.ts
+++ b/packages/tendermint-rpc/src/tendermint34/adaptor/responses.ts
@@ -257,13 +257,13 @@ function decodeConsensusParams(data: RpcConsensusParams): responses.ConsensusPar
 // for block results
 interface RpcValidatorUpdate {
   readonly pub_key: RpcPubkey;
-  readonly power: string;
+  readonly power?: string;
 }
 
 export function decodeValidatorUpdate(data: RpcValidatorUpdate): responses.ValidatorUpdate {
   return {
     pubkey: decodePubkey(assertObject(data.pub_key)),
-    votingPower: Integer.parse(assertNotEmpty(data.power)),
+    votingPower: data.power ? Integer.parse(data.power) : undefined,
   };
 }
 
diff --git a/packages/tendermint-rpc/src/tendermint34/responses.ts b/packages/tendermint-rpc/src/tendermint34/responses.ts
index c9d1ec41..3ae52527 100644
--- a/packages/tendermint-rpc/src/tendermint34/responses.ts
+++ b/packages/tendermint-rpc/src/tendermint34/responses.ts
@@ -356,7 +356,7 @@ export interface Validator {
 
 export interface ValidatorUpdate {
   readonly pubkey: ValidatorPubkey;
-  readonly votingPower: number;
+  readonly votingPower?: number;
 }
 
 export interface ConsensusParams {
diff --git a/packages/tendermint-rpc/src/tendermint35/adaptor/responses.spec.ts b/packages/tendermint-rpc/src/tendermint35/adaptor/responses.spec.ts
index 04bdd6ee..2999791d 100644
--- a/packages/tendermint-rpc/src/tendermint35/adaptor/responses.spec.ts
+++ b/packages/tendermint-rpc/src/tendermint35/adaptor/responses.spec.ts
@@ -49,6 +49,26 @@ describe("Adaptor Responses", () => {
         votingPower: 11418237,
       });
     });
+
+    it("works for block results format without voting power", () => {
+      // from https://rpc.cosmos.network/block_results?height=10883046
+      const update = decodeValidatorUpdate({
+        pub_key: {
+          Sum: {
+            type: "tendermint.crypto.PublicKey_Ed25519",
+            value: {
+              ed25519: "HjSC7VkhKih6xMhudlqfaFE8ZZnP8RKJPv4iqR7RhcE="
+            }
+          }
+        }
+      });
+      expect(update).toEqual({
+        pubkey: {
+          algorithm: "ed25519",
+          data: fromBase64("HjSC7VkhKih6xMhudlqfaFE8ZZnP8RKJPv4iqR7RhcE="),
+        },
+      });
+    });
   });
 
   describe("decodeValidatorInfo", () => {
diff --git a/packages/tendermint-rpc/src/tendermint35/adaptor/responses.ts b/packages/tendermint-rpc/src/tendermint35/adaptor/responses.ts
index 6fa99446..90b2db0b 100644
--- a/packages/tendermint-rpc/src/tendermint35/adaptor/responses.ts
+++ b/packages/tendermint-rpc/src/tendermint35/adaptor/responses.ts
@@ -259,13 +259,13 @@ function decodeConsensusParams(data: RpcConsensusParams): responses.ConsensusPar
 // for block results
 interface RpcValidatorUpdate {
   readonly pub_key: RpcPubkey;
-  readonly power: string;
+  readonly power?: string;
 }
 
 export function decodeValidatorUpdate(data: RpcValidatorUpdate): responses.ValidatorUpdate {
   return {
     pubkey: decodePubkey(assertObject(data.pub_key)),
-    votingPower: Integer.parse(assertNotEmpty(data.power)),
+    votingPower: data.power ? Integer.parse(data.power) : undefined,
   };
 }
 
diff --git a/packages/tendermint-rpc/src/tendermint35/responses.ts b/packages/tendermint-rpc/src/tendermint35/responses.ts
index d1e9f5a8..be2eecca 100644
--- a/packages/tendermint-rpc/src/tendermint35/responses.ts
+++ b/packages/tendermint-rpc/src/tendermint35/responses.ts
@@ -361,7 +361,7 @@ export interface Validator {
 
 export interface ValidatorUpdate {
   readonly pubkey: ValidatorPubkey;
-  readonly votingPower: number;
+  readonly votingPower?: number;
 }
 
 export interface ConsensusParams {