grafana/k6 · error

env var ' ' is not a valid boolean value

Error message

env var '%s' is not a valid boolean value: %w

What it means

Boolean runtime options can be set from the environment; saveBoolFromEnv parses K6_INCLUDE_SYSTEM_ENV_VARS and K6_NO_THRESHOLDS with strconv.ParseBool. Only 1, t, T, TRUE, true, True, 0, f, F, FALSE, false, False are accepted — anything else ('yes', 'on', 'enable') aborts startup with this error naming the offending variable. An explicitly set CLI flag is not overridden by the env value.

Solutions

1. Use an accepted boolean literal: K6_NO_THRESHOLDS=true (or 1/0)
2. Unset the variable if you don't need the option
3. Fix the definition in the env file / CI settings that injected the bad value

Example fix

# before
K6_NO_THRESHOLDS=yes k6 run script.js

# after
K6_NO_THRESHOLDS=true k6 run script.js

# preflight boolean env vars accepted by Go's ParseBool
check_bool_env() {
  v="${!1:-}"
  [ -z "$v" ] && return 0
  case "${v,,}" in
    1|t|true|0|f|false) return 0;;
    *) echo "$1=$v is not a valid boolean (use true/false/1/0)" >&2; return 1;;
  esac
}
check_bool_env K6_NO_THRESHOLDS && check_bool_env K6_INCLUDE_SYSTEM_ENV_VARS || exit 1
k6 run script.js

When it happens

Trigger: K6_NO_THRESHOLDS=yes k6 run script.js; K6_INCLUDE_SYSTEM_ENV_VARS=on; docker-compose env files or CI variables using yes/no conventions.

Common situations: Porting configuration from tools that accept yes/no or on/off; hand-edited .env files; variable reused across tools with different boolean syntaxes.

Understand the failure class

Background: "is not a valid" / "Invalid ... value" environment variable errors: how libraries validate env vars and what to do when they reject yours — this error's family across 48 libraries.

Related errors

• failed to initialize cloud secret source
• invalid environment variable name
• a function is expected as the second argument of…
• both K6_CLOUD_METRICS_PUSH_URL and K6_CLOUD_TEST_RUN_TOKEN…
• can't have two secret sources that are default ones, second…

AI-assisted analysis of grafana/k6@01ffac6f24 (2026-08-18). Data as JSON: /api/errors/c7a9e452839f09e3. Report an issue: GitHub.

Appendix: source

Thrown at internal/cmd/runtime_options.go:159

		opts.TracesOutput = null.StringFrom(envVar)
	}

	// If enabled, gather the actual system environment variables
	if opts.IncludeSystemEnvVars.Bool {
		opts.Env = environment
	}

	return opts, nil
}

func saveBoolFromEnv(env map[string]string, varName string, placeholder *null.Bool) error {
	strValue, ok := env[varName]
	if !ok {
		return nil
	}
	val, err := strconv.ParseBool(strValue)
	if err != nil {
		return fmt.Errorf("env var '%s' is not a valid boolean value: %w", varName, err)
	}
	// Only override if not explicitly set via the CLI flag
	if !placeholder.Valid {
		*placeholder = null.BoolFrom(val)
	}
	return nil
}

View on GitHub (pinned to 01ffac6f24)