diff --git a/abci/types/types.go b/abci/types/types.go
index d13947d1a..121e72159 100644
--- a/abci/types/types.go
+++ b/abci/types/types.go
@@ -5,6 +5,9 @@ import (
 	"encoding/json"
 
 	"github.com/gogo/protobuf/jsonpb"
+	"github.com/tendermint/tendermint/crypto"
+	"github.com/tendermint/tendermint/crypto/encoding"
+	"github.com/tendermint/tendermint/internal/jsontypes"
 )
 
 const (
@@ -135,6 +138,48 @@ func (r *EventAttribute) UnmarshalJSON(b []byte) error {
 	return jsonpbUnmarshaller.Unmarshal(reader, r)
 }
 
+// validatorUpdateJSON is the JSON encoding of a validator update.
+//
+// It handles translation of public keys from the protobuf representation to
+// the legacy Amino-compatible format expected by RPC clients.
+type validatorUpdateJSON struct {
+	PubKey json.RawMessage `json:"pub_key,omitempty"`
+	Power  int64           `json:"power,string"`
+}
+
+func (v *ValidatorUpdate) MarshalJSON() ([]byte, error) {
+	key, err := encoding.PubKeyFromProto(v.PubKey)
+	if err != nil {
+		return nil, err
+	}
+	jkey, err := jsontypes.Marshal(key)
+	if err != nil {
+		return nil, err
+	}
+	return json.Marshal(validatorUpdateJSON{
+		PubKey: jkey,
+		Power:  v.GetPower(),
+	})
+}
+
+func (v *ValidatorUpdate) UnmarshalJSON(data []byte) error {
+	var vu validatorUpdateJSON
+	if err := json.Unmarshal(data, &vu); err != nil {
+		return err
+	}
+	var key crypto.PubKey
+	if err := jsontypes.Unmarshal(vu.PubKey, &key); err != nil {
+		return err
+	}
+	pkey, err := encoding.PubKeyToProto(key)
+	if err != nil {
+		return err
+	}
+	v.PubKey = pkey
+	v.Power = vu.Power
+	return nil
+}
+
 // Some compile time assertions to ensure we don't
 // have accidental runtime surprises later on.
 
diff --git a/rpc/coretypes/responses_test.go b/rpc/coretypes/responses_test.go
index d4ced795a..bf66db0c9 100644
--- a/rpc/coretypes/responses_test.go
+++ b/rpc/coretypes/responses_test.go
@@ -1,10 +1,18 @@
 package coretypes
 
 import (
+	"bytes"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
+	abci "github.com/tendermint/tendermint/abci/types"
+	pbcrypto "github.com/tendermint/tendermint/proto/tendermint/crypto"
 	"github.com/tendermint/tendermint/types"
 )
 
@@ -33,3 +41,53 @@ func TestStatusIndexer(t *testing.T) {
 		assert.Equal(t, tc.expected, status.TxIndexEnabled())
 	}
 }
+
+// A regression test for https://github.com/tendermint/tendermint/issues/8583.
+func TestResultBlockResults_regression8583(t *testing.T) {
+	const keyData = "0123456789abcdef0123456789abcdef" // 32 bytes
+	wantKey := base64.StdEncoding.EncodeToString([]byte(keyData))
+
+	rsp := &ResultBlockResults{
+		ValidatorUpdates: []abci.ValidatorUpdate{{
+			PubKey: pbcrypto.PublicKey{
+				Sum: &pbcrypto.PublicKey_Ed25519{Ed25519: []byte(keyData)},
+			},
+			Power: 400,
+		}},
+	}
+
+	// Use compact here so the test data remain legible. The output from the
+	// marshaler will have whitespace folded out so we need to do that too for
+	// the comparison to be valid.
+	var buf bytes.Buffer
+	require.NoError(t, json.Compact(&buf, []byte(fmt.Sprintf(`
+{
+  "height": "0",
+  "txs_results": null,
+  "total_gas_used": "0",
+  "finalize_block_events": null,
+  "validator_updates": [
+    {
+      "pub_key":{"type": "tendermint/PubKeyEd25519", "value": "%s"},
+      "power": "400"
+    }
+  ],
+  "consensus_param_updates": null
+}`, wantKey))))
+
+	bits, err := json.Marshal(rsp)
+	if err != nil {
+		t.Fatalf("Encoding block result: %v", err)
+	}
+	if diff := cmp.Diff(buf.String(), string(bits)); diff != "" {
+		t.Errorf("Marshaled result (-want, +got):\n%s", diff)
+	}
+
+	back := new(ResultBlockResults)
+	if err := json.Unmarshal(bits, back); err != nil {
+		t.Fatalf("Unmarshaling: %v", err)
+	}
+	if diff := cmp.Diff(rsp, back); diff != "" {
+		t.Errorf("Unmarshaled result (-want, +got):\n%s", diff)
+	}
+}