compose validation Docker Origin: Platform & cloud Last updated 12 Oct 2026

docker compose: services.x Additional property y is not allowed / yaml: line N: mapping values are not allowed

The compose file is invalid YAML or uses a key Compose doesn’t recognise at that level (usually an indentation mistake).

Exact message you may see Additional propertymapping values are not allowed in this contextdid not find expected key
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Seen on: Docker

Meaning

YAML is indentation-sensitive. A key indented one level too far or too little ends up under the wrong parent, producing “Additional property … is not allowed”. Tabs and unquoted colons cause “mapping values are not allowed”.

Common causes

  • Wrong indentation (key under the wrong parent)
  • Tabs instead of spaces
  • Unquoted values containing : (e.g. command strings)
  • Typos in keys (enviroment, port)
  • Old version: / v2-only keys with Compose v2

⚡ Quick fix

  1. Validate: docker compose config
  2. Use 2-space indentation, no tabs
  3. Quote strings containing colons
  4. Check key spelling against the Compose spec

Detailed fix by platform

Docker

  1. Correct structure:
    yaml
    services:
  web:
    image: nginx:1.27
    ports:
      - "8080:80"          # quoted: contains a colon
    environment:
      APP_ENV: production

How to diagnose

  1. Validate — docker compose config output
  2. Line — Which line/key is reported?
  3. Whitespace — Tabs or mixed indentation?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Platform & cloud. Errors that are often confused with or caused by this one (click to open):

.gitlab-ci.yml invalid — GitLab CI: Found errors in your .gitlab-ci.yml: jobs:build config contains unknown keys: scripts (CI/CD).gitlab-ci.yml invalidConfig compilation failed — CircleCI: Error calling workflow: 'build'. Cannot find a definition for job named test / Config does not conform to schema (CI/CD)Config compilation fa…COPY failed — COPY failed: file not found in build context / "/app/x": not found (Docker)COPY faileddepends on undefined service — service "web" depends on undefined service "db": invalid compose project (Docker)depends on undefined …docker-compose: command not found — docker-compose: command not found / 'compose' is not a docker command (Docker)docker-compose: comma…error converting YAML to JSON — error converting YAML to JSON: yaml: line 12: did not find expected key (Kubernetes)error converting YAML…IndentationError — IndentationError: unexpected indent / expected an indented block (Python)IndentationErrornetwork not found — Error response from daemon: network X not found (Docker)network not foundcompose v…

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