Multiple paths are no longer supported for…

Error message

Multiple paths are no longer supported for PACKER_PLUGIN_PATH.
This should be defined as one of the following options for your environment:
* PACKER_PLUGIN_PATH=%v

What it means

PACKER_PLUGIN_PATH must point to a single plugin directory. Multi-path (colon/semicolon-separated) values were supported in old Packer versions but are no longer allowed, so PluginFolder returns this error when the env var contains the OS path list separator.

Solutions

Set PACKER_PLUGIN_PATH to a single directory and place all plugins there.
Remove the env var entirely to use the default per-user plugin directory.
Split usage: keep one directory and symlink plugins from other locations into it.

Example fix

// before
export PACKER_PLUGIN_PATH=/opt/plugins:$HOME/.packer.d/plugins
// after
export PACKER_PLUGIN_PATH=$HOME/.packer.d/plugins
# or remove it and let Packer use its default discovery paths

Defensive patterns

Strategy: validation

Validate before calling

if v := os.Getenv("PACKER_PLUGIN_PATH"); strings.Contains(v, string(os.PathListSeparator)) {
  return fmt.Errorf("PACKER_PLUGIN_PATH must be a single directory, got %q", v)
}

Try / catch

if dir, err := packer.PluginFolder(); err != nil {
  if strings.Contains(err.Error(), "Multiple paths") {
    // reset PACKER_PLUGIN_PATH to one directory
  }
}

Prevention

Never reuse PATH-style multi-dir exports for PACKER_PLUGIN_PATH.
Use one plugin directory and symlink extras into it.
Unset the variable to fall back to Packer's default discovery paths.

When it happens

Trigger: PluginFolder() in packer/plugin_folders.go detects strings.Contains(envValue, os.PathListSeparator) — e.g. PACKER_PLUGIN_PATH=/opt/plugins:/home/user/plugins (unix) or C:\a;C:\b (windows). Callers include pluginDirectory, RunContext, loadConfig, and Discover.

Common situations: Reusing an old script that set multiple paths when Packer supported them; copying a PATH-style export to PACKER_PLUGIN_PATH; CI configuration combining custom and default plugin dirs.

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

AI-assisted analysis of hashicorp/packer@eb36e3c3e4 (2026-09-05). Data as JSON: /api/errors/1360c8223decb077. Report an issue: GitHub.

Appendix: source

Thrown at packer/plugin_folders.go:22

package packer

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"

	"github.com/hashicorp/packer-plugin-sdk/pathing"
)

var pathSep = fmt.Sprintf("%c", os.PathListSeparator)

// PluginFolder returns the known plugin folder based on system.
func PluginFolder() (string, error) {
	if packerPluginPath := os.Getenv("PACKER_PLUGIN_PATH"); packerPluginPath != "" {
		if strings.Contains(packerPluginPath, pathSep) {
			return "", fmt.Errorf("Multiple paths are no longer supported for PACKER_PLUGIN_PATH.\n"+
				"This should be defined as one of the following options for your environment:"+
				"\n* PACKER_PLUGIN_PATH=%v", strings.Join(strings.Split(packerPluginPath, pathSep), "\n* PACKER_PLUGIN_PATH="))
		}

		return packerPluginPath, nil
	}

	cd, err := pathing.ConfigDir()
	if err != nil {
		log.Printf("[ERR] Error loading config directory: %v", err)
		return "", err
	}

	return filepath.Join(cd, "plugins"), nil
}

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