'defaultValue' property is missing at the ${j} index of the

Error message

'defaultValue' property is missing at the ${j} index of the 'forms' property in ${file}.

What it means

Field configs (unlike form components) require a 'defaultValue' property so the admin can initialize the field. When a field object inside 'fields' lacks defaultValue, the plugin warns with the entry index and file, then skips that entry.

Source

Thrown at packages/admin/admin-vite-plugin/src/custom-fields/generate-custom-field-forms.ts:628

      ) {
        logger.warn(
          `'${name}' property in the 'fields' property at the ${j} index of the 'forms' property in ${file} is malformed. The property must be an object or a call to form.define().`,
          { file }
        )
        return
      }

      const fieldObject = isObjectExpression(field.value)
        ? field.value
        : (field.value.arguments[0] as ObjectExpression)

      const defaultValueProperty = fieldObject.properties.find(
        (p) =>
          isObjectProperty(p) && isIdentifier(p.key, { name: "defaultValue" })
      ) as ObjectProperty | undefined

      if (!defaultValueProperty) {
        logger.warn(
          `'defaultValue' property is missing at the ${j} index of the 'forms' property in ${file}.`,
          { file }
        )
        return
      }

      const validationProperty = fieldObject.properties.find(
        (p) =>
          isObjectProperty(p) && isIdentifier(p.key, { name: "validation" })
      ) as ObjectProperty | undefined

      if (!validationProperty) {
        logger.warn(
          `'validation' property is missing at the ${j} index of the 'forms' property in ${file}.`,
          { file }
        )
        return
      }

View on GitHub (pinned to 5e06e544a2)

Solutions

Add defaultValue to the field object, e.g. defaultValue: '' or defaultValue: null
Give every field in 'fields' both defaultValue and validation
Use form.define({ defaultValue, validation }) for clarity

Example fix

// before
fields: { myField: { validation: (v) => v.length > 2 } }
// after
fields: { myField: { defaultValue: '', validation: (v) => v.length > 2 } }

Defensive patterns

Strategy: validation

Validate before calling

Object.entries(f.fields).forEach(([name, def]) => {
  if (typeof def !== 'object' || !('defaultValue' in def)) {
    throw new Error(`field '${name}' is missing defaultValue`)
  }
})

Type guard

const hasDefaultValue = (d: unknown): d is { defaultValue: unknown } =>
  typeof d === 'object' && d !== null && 'defaultValue' in (d as object)

Prevention

Always write defaultValue and validation together for every field config

When it happens

Trigger: fields: { myField: { validation: ... } } where the object has validation but no defaultValue key.

Common situations: Assuming defaultValue is optional, porting form.define component configs (which don't need it) into the config flow, or forgetting the key when hand-writing configs.

Related errors

AI-assisted analysis of medusajs/medusa@5e06e544a2 (2026-08-27). Data as JSON: /api/errors/4eddaf5fcc954cf1. Report an issue: GitHub.