How to fix NOPROTO sorry, this protocol version is not supported in Redis

RedisINTERMEDIATEMEDIUMUpdated Dec 15, 2025· 277 views

Redis returns `NOPROTO sorry, this protocol version is not supported` when a client tries to negotiate an unsupported protocol version during the HELLO handshake, typically when requesting RESP3 on a server that only supports RESP2. Modern clients auto-negotiate to RESP3 by default, but older Redis versions or disabled RESP3 configurations reject this upgrade. This guide explains the protocol mismatch, common scenarios, and how to downgrade or enable the correct protocol version.

Quick fix

Fixes NOPROTO

# Check Redis version
redis-cli INFO server | grep redis_version

# Test if HELLO command is supported
redis-cli HELLO 3

# Expected output if RESP3 is supported:
# 1) "server"
# 2) "redis"
# 3) "version"
# 4) "7.2.0"
# ...

# If RESP3 is not supported, you'll see:
# (error) NOPROTO sorry, this protocol version is not supported
# OR
# (error) ERR unknown command 'HELLO'
  1. Check the Redis server version and RESP3 support
  2. Configure the client to use RESP2 explicitly
  3. Enable RESP3 on the Redis server if available
  4. Update the client library to handle NOPROTO gracefully
redis — error
# Check Redis version
redis-cli INFO server | grep redis_version
# Test if HELLO command is supported
redis-cli HELLO 3
# Expected output if RESP3 is supported:
# 1) "server"
# 2) "redis"
# 3) "version"
# 4) "7.2.0"
# ...
# If RESP3 is not supported, you'll see:
# (error) NOPROTO sorry, this protocol version is not supported
# OR
# (error) ERR unknown command 'HELLO'
NOPROTO sorry, this protocol version is not supported

What this error means

When Redis responds with "NOPROTO sorry, this protocol version is not supported," it means the client issued a `HELLO` command requesting a specific RESP (REdis Serialization Protocol) version that the server does not support. The HELLO command is used during connection handshake to negotiate protocol capabilities—clients typically send `HELLO 3` to request RESP3 features, but if the server only implements RESP2 or has RESP3 disabled, it returns this error. This error is part of the RESP3 specification and indicates a version mismatch between client and server. Redis 6.0+ introduced RESP3, and Redis 7.2+ enabled it by default for new databases, but existing databases upgraded to 7.2 may have RESP3 disabled for compatibility. The client must handle this error by falling back to RESP2 or the user must configure the server to support the requested version.

Typical symptoms

  • Connection fails immediately after client startup with `NOPROTO sorry, this protocol version is not supported` error
  • Applications using Lettuce (Java), go-redis v9+, or node-redis with RESP3 enabled cannot connect to older Redis instances
  • Redis logs show clients attempting `HELLO 3` or `HELLO 4` commands that are being rejected
  • Clients that successfully connected to Redis 6.x fail after upgrading to Redis 7.2 with RESP3 disabled
  • Error occurs specifically during handshake phase before any application commands are executed

Common causes

  1. The client library defaults to RESP3 (e.g., go-redis v9+, Lettuce 6+, node-redis with protocol: 3) but the Redis server is version 5.x or earlier, which only supports RESP2
  2. Redis 7.2 server has RESP3 explicitly disabled via configuration (common for databases upgraded from earlier versions to maintain backward compatibility)
  3. Client requests an invalid or future protocol version (e.g., `HELLO 4`) that no current Redis version implements
  4. The client library has a bug and does not handle NOPROTO gracefully by falling back to RESP2, instead failing the connection entirely
  5. Redis cluster or proxy (like Twemproxy) in the connection path does not support RESP3 protocol negotiation

How to fix "NOPROTO sorry, this protocol version is not supported"

1Check the Redis server version and RESP3 support

Connect to the Redis server and verify its version and protocol capabilities:

bash
# Check Redis version
redis-cli INFO server | grep redis_version

# Test if HELLO command is supported
redis-cli HELLO 3

# Expected output if RESP3 is supported:
# 1) "server"
# 2) "redis"
# 3) "version"
# 4) "7.2.0"
# ...

# If RESP3 is not supported, you'll see:
# (error) NOPROTO sorry, this protocol version is not supported
# OR
# (error) ERR unknown command 'HELLO'

If the version is below 6.0, RESP3 is not available. If it's 7.2+ but returns NOPROTO, RESP3 may be disabled in configuration.

2Configure the client to use RESP2 explicitly

Most modern Redis clients support protocol version configuration. Set it to RESP2 to avoid the handshake error:

Node.js (node-redis v4+):

javascript
import { createClient } from 'redis';

const client = createClient({
  url: 'redis://localhost:6379',
  // Force RESP2
  RESP: 2
});

await client.connect();

Go (go-redis v9+):

go
import "github.com/redis/go-redis/v9"

client := redis.NewClient(&redis.Options{
    Addr:     "localhost:6379",
    Protocol: 2, // Force RESP2
})

Java (Lettuce 6+):

java
RedisURI redisUri = RedisURI.Builder
    .redis("localhost", 6379)
    .build();

RedisClient client = RedisClient.create(redisUri);
// Lettuce should auto-fallback on NOPROTO, but you can disable RESP3:
client.setOptions(ClientOptions.builder()
    .protocolVersion(ProtocolVersion.RESP2)
    .build());

Check your client library documentation for the exact option name (protocol, RESP, protocolVersion).

3Enable RESP3 on the Redis server if available

If your Redis version is 7.2+ and RESP3 is disabled, you can enable it via configuration or during database creation:

For Redis Enterprise/Cloud (upgraded databases):
RESP3 may be disabled by default on databases upgraded from earlier versions. Check with your provider or create a new database instance that has RESP3 enabled by default.

For self-hosted Redis 7.2+:
There is no explicit redis.conf setting to disable RESP3—it should be available by default. If HELLO 3 still fails, verify:

bash
# Ensure no custom module or proxy is blocking HELLO
redis-cli COMMAND INFO HELLO

# Check for any custom command rename/disable in redis.conf
grep -i "rename-command" /etc/redis/redis.conf

If using a Redis cluster or proxy like Twemproxy, upgrade to versions that support RESP3 or continue using RESP2 on the client.

4Update the client library to handle NOPROTO gracefully

Older client versions may not implement automatic fallback from RESP3 to RESP2. Upgrade to the latest stable version:

bash
# Node.js
npm install redis@latest

# Python
pip install --upgrade redis

# Go
go get github.com/redis/go-redis/v9@latest

# Java (Maven)
# Update pom.xml to Lettuce 6.3+ which includes better NOPROTO handling

Lettuce versions 6.3+ and go-redis v9.3+ implement automatic protocol downgrade when receiving NOPROTO, so the connection retries with RESP2 without user intervention. Check the release notes for your client library to confirm this feature is included.

Advanced notes

The RESP3 specification defines NOPROTO as the correct error response when a requested protocol version is unavailable, but older Redis versions (pre-6.0) return -ERR unknown command 'HELLO' instead because the HELLO command itself doesn't exist. Clients must handle both error types to maintain backward compatibility.

Redis 7.2 introduced a breaking change for some deployments: upgraded databases (not freshly created) have RESP3 disabled to prevent compatibility issues, but the error response changed from -ERR unknown command 'HELLO' to -NOPROTO, which broke Lettuce and other clients that only checked for the former. This led to GitHub issues like lettuce#2170 and lettuce#2455, prompting client libraries to implement automatic RESP2 fallback on any HELLO failure.

When debugging, note that RESP3 provides significant benefits (push events, better type mapping, out-of-band data) but is not required for most workloads. If you control both client and server, enabling RESP3 is recommended for new deployments, but forcing RESP2 is a safe and pragmatic solution for legacy or managed Redis instances.

Frequently asked questions

What does "NOPROTO" mean?
When Redis responds with "NOPROTO sorry, this protocol version is not supported," it means the client issued a HELLO command requesting a specific RESP (REdis Serialization Protocol) version that the server does not support. The HELLO command is used during connection handshake to negotiate protocol capabilities—clients typically send HELLO 3 to request RESP3 features, but if the server only implements RESP2 or has RESP3 disabled, it returns this error. This error is part of the RESP3 specification and indicates a version mismatch between client and server.
How do I fix "NOPROTO"?
Redis returns NOPROTO sorry, this protocol version is not supported when a client tries to negotiate an unsupported protocol version during the HELLO handshake, typically when requesting RESP3 on a server that only supports RESP2. Modern clients auto-negotiate to RESP3 by default, but older Redis versions or disabled RESP3 configurations reject this upgrade. This guide explains the protocol mismatch, common scenarios, and how to downgrade or enable the correct protocol version.
What causes "NOPROTO"?
The client library defaults to RESP3 (e.g., go-redis v9+, Lettuce 6+, node-redis with protocol: 3) but the Redis server is version 5.x or earlier, which only supports RESP2 Redis 7.2 server has RESP3 explicitly disabled via configuration (common for databases upgraded from earlier versions to maintain backward compatibility) Client requests an invalid or future protocol version (e.g., HELLO 4) that no current Redis version implements
Is the "NOPROTO" error serious?
It is a medium-severity error — more of a blocker than a risk. The steps above resolve it.

Official resources & further reading