Package version '# ' includes dashes, converting to…

Error message

Package version '#{@version}' includes dashes, converting to underscores

What it means

RPM's Version field must not contain dashes; rpmbuild rejects them. When the rpm output target sees a String version containing '-', it rewrites every dash to an underscore in place and logs this warning. The package still builds, but its version metadata differs from the string you passed.

Solutions

Strip or replace dashes before invoking fpm: `VER=${VER//-/_}`
Split semver prereleases the RPM way: `--version 1.2.3 --iteration 0.1.beta1`
Derive the version from the tag only, e.g. `git describe --tags --abbrev=0`, not the full describe string

Example fix

# before
fpm -s dir -t rpm -n app -v $(git describe --tags) .

# after
fpm -s dir -t rpm -n app -v $(git describe --tags --abbrev=0) --iteration $(git rev-list --count HEAD) .

Defensive patterns

Strategy: validation

Validate before calling

VER="${VER//-/_}"
if [[ "$VER" == *-* ]]; then
  echo "version contains dashes after sanitize: $VER" >&2
  exit 1
fi

Type guard

def rpm_safe_version?(str)
  str.is_a?(String) && !str.include?('-') && !str.empty?
end

Prevention

Use `git describe --tags --abbrev=0` (tag only) for --version, and put the commit count into --iteration
Put semver prerelease suffixes in --iteration with underscores, per RPM convention
Assert the published rpm's %{VERSION} matches the intended tag in CI

When it happens

Trigger: Building an rpm with `--version 1.2.3-beta.1`, or with `--version $(git describe --tags)` which yields '1.2.3-14-g0abc1' that then becomes '1.2.3_14_g0abc1'.

Common situations: CI pipelines feeding git describe or npm/python prerelease versions straight into fpm; downstream tools comparing versions mismatch because the published rpm carries underscores where the tag had dashes.

Related errors

AI-assisted analysis of jordansissel/fpm@b6d77ba72a (2026-08-21). Data as JSON: /api/errors/cacf4ebedb4df133. Report an issue: GitHub.

Appendix: source

Thrown at lib/fpm/package/rpm.rb:640

    end
  end # def prefix

  def build_sub_dir
    return "BUILD"
    #return File.join("BUILD", prefix)
  end # def build_sub_dir

  def summary
    if !attributes[:rpm_summary]
      return @description.split("\n").find { |line| !line.strip.empty? } || "_"
    end

    return attributes[:rpm_summary]
  end # def summary

  def version
    if @version.kind_of?(String) and @version.include?("-")
      logger.warn("Package version '#{@version}' includes dashes, converting" \
                   " to underscores")
      @version = @version.gsub(/-/, "_")
    end

    return @version
  end

  # The default epoch value must be nil, see #381
  def epoch
    return @epoch if @epoch.is_a?(Numeric)

    if @epoch.nil? or @epoch.empty?
      return nil
    end

    return @epoch
  end # def epoch

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