diff --git a/substrate/substrate-dump/src/dumper.ts b/substrate/substrate-dump/src/dumper.ts
index 04eac4cf2..5eac02d6e 100644
--- a/substrate/substrate-dump/src/dumper.ts
+++ b/substrate/substrate-dump/src/dumper.ts
@@ -27,7 +27,7 @@ export interface DumperOptions {
     lastBlock?: number
     withTrace?: boolean | string
     chunkSize: number
-    metricsPort?: number
+    metrics?: number
 }
 
 
@@ -86,7 +86,7 @@ export class Dumper {
 
     @def
     prometheus() {
-        return new PrometheusServer(this.options.metricsPort ?? 3000);
+        return new PrometheusServer(this.options.metrics ?? 0, this.rpc())
     }
 
     ingest(range: Range): AsyncIterable<BlockBatch> {
@@ -99,11 +99,10 @@ export class Dumper {
                 : this.options.withTrace ? '' : undefined
         }
 
-        const blocks = this.src().getFinalizedBlocks([{
+        return this.src().getFinalizedBlocks([{
             range,
             request
         }])
-        return blocks;
     }
 
     private async *process(from?: number, prevHash?: string): AsyncIterable<BlockData[]> {
@@ -115,7 +114,7 @@ export class Dumper {
 
         let height = new Throttler(() => this.src().getFinalizedHeight(), 300_000)
         let chainHeight = await height.get()
-        this.prometheus().setChainHeight(chainHeight);
+        this.prometheus().setChainHeight(chainHeight)
 
         let progress = new Progress({
             initialValue: this.range().from,
@@ -141,9 +140,6 @@ export class Dumper {
                     )
                 }
             }
-            const metrics = this.rpc().getMetrics();
-            this.prometheus().setSuccesfulRequestCount(metrics.requestsServed);
-            this.prometheus().setFailedRequestCount(metrics.connectionErrors);
 
             yield batch.blocks
 
@@ -206,16 +202,16 @@ export class Dumper {
             }
         } else {
             const archive = new ArchiveLayout(this.fs())
-            const prometheus = this.prometheus();
-            if (this.options.metricsPort) {
-                await prometheus.serve();
-                this.log().info(`prometheus metrics are available on port ${this.options.metricsPort}`)
+            const prometheus = this.prometheus()
+            if (this.options.metrics != null) {
+                const promServer = await prometheus.serve()
+                this.log().info(`prometheus metrics are available on port ${promServer.port}`)
             }
             await archive.appendRawBlocks({
                 blocks: (nextBlock, prevHash) => this.saveMetadata(this.process(nextBlock, prevHash)),
                 range: this.range(),
                 chunkSize: this.options.chunkSize * 1024 * 1024,
-                onSuccessWrite: ({ blockRange: { to } }) => { prometheus.setLastWrittenBlock(to.height); }
+                onSuccessWrite: ({ blockRange: { to } }) => { prometheus.setLastWrittenBlock(to.height) }
             })
         }
     }
diff --git a/substrate/substrate-dump/src/main.ts b/substrate/substrate-dump/src/main.ts
index 0a883c084..b1af928e1 100644
--- a/substrate/substrate-dump/src/main.ts
+++ b/substrate/substrate-dump/src/main.ts
@@ -22,7 +22,7 @@ runProgram(() => {
     program.option('--last-block <number>', 'Height of the last block to dump', nat)
     program.option('--with-trace [targets]', 'Fetch block trace')
     program.option('--chunk-size <MB>', 'Data chunk size in megabytes', positiveInt, 32)
-    program.option('--metrics-port <port>', 'Port to serve metrics on', nat)
+    program.option('--metrics <port>', 'Enable prometheus metrics server', nat)
 
     let args = program.parse().opts() as DumperOptions
 
diff --git a/substrate/substrate-dump/src/prometheus.ts b/substrate/substrate-dump/src/prometheus.ts
index 4316781c4..a969bfc42 100644
--- a/substrate/substrate-dump/src/prometheus.ts
+++ b/substrate/substrate-dump/src/prometheus.ts
@@ -1,3 +1,4 @@
+import { RpcClient } from '@subsquid/rpc-client';
 import {createPrometheusServer, ListeningServer} from '@subsquid/util-internal-prometheus-server'
 import promClient, { collectDefaultMetrics, Gauge, Registry } from 'prom-client';
 
@@ -9,7 +10,7 @@ export class PrometheusServer {
     private lastWrittenBlockGauge: Gauge;
     private rpcRequestsGauge: Gauge;
 
-    constructor(port: number) {
+    constructor(port: number, rpc: RpcClient) {
         this.port = port;
         this.chainHeightGauge = new Gauge({
             name: 'sqd_dump_chain_height',
@@ -27,7 +28,16 @@ export class PrometheusServer {
             name: 'sqd_rpc_requests_count',
             help: 'Number of rpc requests of different kinds',
             labelNames: ['kind'],
-            registers: [this.registry]
+            registers: [this.registry],
+            collect() {
+                const metrics = rpc.getMetrics();
+                this.set({
+                    kind: 'successful'
+                }, metrics.requestsServed);
+                this.set({
+                    kind: 'failed'
+                }, metrics.connectionErrors);
+            }
         });
 
         collectDefaultMetrics({register: this.registry})
@@ -41,18 +51,6 @@ export class PrometheusServer {
         this.lastWrittenBlockGauge.set(block);
     }
 
-    setSuccesfulRequestCount(requests: number) {
-        this.rpcRequestsGauge.set({
-            'kind': 'successful'
-        }, requests)
-    }
-
-    setFailedRequestCount(requests: number) {
-        this.rpcRequestsGauge.set({
-            'kind': 'failed'
-        }, requests)
-    }
-
     serve(): Promise<ListeningServer> {
         return createPrometheusServer(this.registry, this.port)
     }
diff --git a/util/util-internal-archive-layout/src/layout.ts b/util/util-internal-archive-layout/src/layout.ts
index 9ffdc217a..bf4285c1f 100644
--- a/util/util-internal-archive-layout/src/layout.ts
+++ b/util/util-internal-archive-layout/src/layout.ts
@@ -193,13 +193,12 @@ export class ArchiveLayout {
                     const chunk = getNextChunk(blockRange.from, blockRange.to)
                     chunk.transactDir('.', async fs => {
                         let content = await out.end()
-                        const writeResult = fs.write('blocks.jsonl.gz', content)
-                        writeResult.then(() => args.onSuccessWrite ? args.onSuccessWrite({
-                            chunk: chunk.abs(),
-                            blockRange
-                        }) : null)
-                        return writeResult
-                    })
+                        return fs.write('blocks.jsonl.gz', content)
+                    }).then(() => args.onSuccessWrite?.({
+                        chunk: chunk.abs(),
+                        blockRange
+                    }))
+
                     firstBlock = undefined
                     lastBlock = undefined
                     out = new GzipBuffer()