What causes "invalid previous version %v@%v" in golang/go?

Ensure the module's current version in go.mod / cache is a valid canonical semver (vMAJOR.MINOR.PATCH[-pre][+build]).

invalid previous version %v@%v

Error message

invalid previous version %v@%v

What it means

Returned by queryProxy at the start of a proxy query when a 'current' version string was supplied that is non-empty, not the literal 'none', and fails gover.ModIsValid. It guards the rest of the query logic against operating on a non-semver current version (e.g. a bare revision hash or malformed string).

Source

Thrown at src/cmd/go/internal/modload/query.go:205

type AllowedFunc func(context.Context, module.Version) error

var errQueryDisabled error = queryDisabledError{}

type queryDisabledError struct{}

func (queryDisabledError) Error() string {
	if cfg.BuildModReason == "" {
		return fmt.Sprintf("cannot query module due to -mod=%s", cfg.BuildMod)
	}
	return fmt.Sprintf("cannot query module due to -mod=%s\n\t(%s)", cfg.BuildMod, cfg.BuildModReason)
}

func queryProxy(ld *Loader, ctx context.Context, proxy, path, query, current string, allowed AllowedFunc, reuse map[module.Version]*modinfo.ModulePublic) (*modfetch.RevInfo, error) {
	ctx, span := trace.StartSpan(ctx, "modload.queryProxy "+path+" "+query)
	defer span.Done()

	if current != "" && current != "none" && !gover.ModIsValid(path, current) {
		return nil, fmt.Errorf("invalid previous version %v@%v", path, current)
	}
	if cfg.BuildMod == "vendor" {
		return nil, errQueryDisabled
	}
	if allowed == nil {
		allowed = func(context.Context, module.Version) error { return nil }
	}

	if ld.MainModules.Contains(path) && (query == "upgrade" || query == "patch") {
		m := module.Version{Path: path}
		if err := allowed(ctx, m); err != nil {
			return nil, fmt.Errorf("internal error: main module version is not allowed: %w", err)
		}
		return &modfetch.RevInfo{Version: m.Version}, nil
	}

	if path == "std" || path == "cmd" {
		return nil, fmt.Errorf("can't query specific version (%q) of standard-library module %q", query, path)

View on GitHub (pinned to b6b368adc5)

Solutions

Ensure the module's current version in go.mod / cache is a valid canonical semver (vMAJOR.MINOR.PATCH[-pre][+build]).
Run 'go get <module>@<valid-semver>' to replace the bad current version with a clean one.
Clear the offending cache entry with 'go clean -modcache' and re-resolve.

Example fix

// before
// error: invalid previous version example.com/pkg@main

// after
$ go get example.com/pkg@v1.2.3

Defensive patterns

Strategy: validation

Validate before calling

// Validate a current version is well-formed before passing to queryProxy:
//   if current != "" && current != "none" && !gover.ModIsValid(path, current) {
//       return fmt.Errorf("refusing to query: bad current version %q", current)
//   }

Type guard

func isValidCurrentVersion(path, current string) bool {
    return current == "" || current == "none" || gover.ModIsValid(path, current)
}

Prevention

Never store non-semver strings (branches, SHAs) as a module's current version in go.mod.
When scripting queries, canonicalize the current version with module.CanonicalVersion first.
Run 'go mod tidy' to normalize versions in go.mod into canonical semver.

When it happens

Trigger: A go command invokes queryProxy with a current version that is not valid semantic version syntax — e.g. a commit SHA, a branch name, or a malformed string recorded as the module's current version.

Common situations: A go.mod or module cache entry holds a non-semver current version; a custom caller of the internal query API passes an unchecked string; a VCS pseudo-version got corrupted.

Related errors

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/6b6a094f18f71bfb. Report an issue: GitHub.