cloudflare/cloudflared · error

expected string found %T for

Error message

expected string found %T for %s

What it means

Type-mismatch error in configFileSettings.String: the named config-file setting exists but is not a string in the parsed YAML (e.g. an int or bool). The typed accessor returns the zero string plus this error rather than coercing the value.

Solutions

1. Quote the value in the config file so it parses as a string (hostname: "example.com").
2. Fix the key name if the wrong setting is being requested.
3. At the call site, use the typed getter matching the actual type shown in %T and convert explicitly.

Example fix

// before (config.yml)
protocol: 2
// after
protocol: "h2mux"

// Go
typeAssertString := func(v interface{}) (string, bool) { s, ok := v.(string); return s, ok }

func asString(v interface{}) (string, bool) { s, ok := v.(string); return s, ok }

s, err := settings.String("hostname")
if err != nil {
    log.Printf("'hostname' must be a quoted string: %v", err)
    return err
}

When it happens

Trigger: Calling String(name) on a setting stored as an int, bool, or slice — e.g. `hostname: 8080` or a boolean flag read as a string.

Common situations: YAML unquoted values that look numeric or boolean (port: 8080, enabled: true) but are consumed as strings; keys confused between sections of the config.

Related errors

• expected duration found %T for
• expected float found %T for
• expected int found %T for
• expected int, found %T for
• expected string, found %T for

AI-assisted analysis of cloudflare/cloudflared@2253eeeb25 (2026-09-06). Data as JSON: /api/errors/63e2fdabc7c2feac. Report an issue: GitHub.

Appendix: source

Thrown at config/configuration.go:317

	return 0, nil
}

func (c *configFileSettings) Float64(name string) (float64, error) {
	if raw, ok := c.Settings[name]; ok {
		if v, ok := raw.(float64); ok {
			return v, nil
		}
		return 0, fmt.Errorf("expected float found %T for %s", raw, name)
	}
	return 0, nil
}

func (c *configFileSettings) String(name string) (string, error) {
	if raw, ok := c.Settings[name]; ok {
		if v, ok := raw.(string); ok {
			return v, nil
		}
		return "", fmt.Errorf("expected string found %T for %s", raw, name)
	}
	return "", nil
}

func (c *configFileSettings) StringSlice(name string) ([]string, error) {
	if raw, ok := c.Settings[name]; ok {
		if slice, ok := raw.([]interface{}); ok {
			strSlice := make([]string, len(slice))
			for i, v := range slice {
				str, ok := v.(string)
				if !ok {
					return nil, fmt.Errorf("expected string, found %T for %v", i, v)
				}
				strSlice[i] = str
			}
			return strSlice, nil
		}
		return nil, fmt.Errorf("expected string slice found %T for %s", raw, name)

View on GitHub (pinned to 2253eeeb25)