diff --git a/cmd/cue/cmd/flags.go b/cmd/cue/cmd/flags.go
index 2ebc90195f5..42d3c601e76 100644
--- a/cmd/cue/cmd/flags.go
+++ b/cmd/cue/cmd/flags.go
@@ -20,38 +20,39 @@ import (
 
 // Common flags
 const (
-	flagAll           flagName = "all"
-	flagAllErrors     flagName = "all-errors"
-	flagCheck         flagName = "check"
-	flagDiff          flagName = "diff"
-	flagDryRun        flagName = "dry-run"
-	flagEscape        flagName = "escape"
-	flagExpression    flagName = "expression"
-	flagExt           flagName = "ext"
-	flagFiles         flagName = "files"
-	flagForce         flagName = "force"
-	flagGlob          flagName = "name"
-	flagIgnore        flagName = "ignore"
-	flagInject        flagName = "inject"
-	flagInjectVars    flagName = "inject-vars"
-	flagInlineImports flagName = "inline-imports"
-	flagJSON          flagName = "json"
-	flagList          flagName = "list"
-	flagMerge         flagName = "merge"
-	flagOut           flagName = "out"
-	flagOutFile       flagName = "outfile"
-	flagPackage       flagName = "package"
-	flagPath          flagName = "path"
-	flagProtoEnum     flagName = "proto_enum"
-	flagProtoPath     flagName = "proto_path"
-	flagRecursive     flagName = "recursive"
-	flagSchema        flagName = "schema"
-	flagSimplify      flagName = "simplify"
-	flagSource        flagName = "source"
-	flagStrict        flagName = "strict"
-	flagTrace         flagName = "trace"
-	flagVerbose       flagName = "verbose"
-	flagWithContext   flagName = "with-context"
+	flagAll             flagName = "all"
+	flagAllErrors       flagName = "all-errors"
+	flagCheck           flagName = "check"
+	flagDiff            flagName = "diff"
+	flagDryRun          flagName = "dry-run"
+	flagEscape          flagName = "escape"
+	flagExpression      flagName = "expression"
+	flagExt             flagName = "ext"
+	flagFiles           flagName = "files"
+	flagForce           flagName = "force"
+	flagGlob            flagName = "name"
+	flagIgnore          flagName = "ignore"
+	flagInject          flagName = "inject"
+	flagInjectVars      flagName = "inject-vars"
+	flagInlineImports   flagName = "inline-imports"
+	flagJSON            flagName = "json"
+	flagLanguageVersion flagName = "language-version"
+	flagList            flagName = "list"
+	flagMerge           flagName = "merge"
+	flagOut             flagName = "out"
+	flagOutFile         flagName = "outfile"
+	flagPackage         flagName = "package"
+	flagPath            flagName = "path"
+	flagProtoEnum       flagName = "proto_enum"
+	flagProtoPath       flagName = "proto_path"
+	flagRecursive       flagName = "recursive"
+	flagSchema          flagName = "schema"
+	flagSimplify        flagName = "simplify"
+	flagSource          flagName = "source"
+	flagStrict          flagName = "strict"
+	flagTrace           flagName = "trace"
+	flagVerbose         flagName = "verbose"
+	flagWithContext     flagName = "with-context"
 
 	// Hidden flags.
 	flagCpuProfile flagName = "cpuprofile"
diff --git a/cmd/cue/cmd/modedit.go b/cmd/cue/cmd/modedit.go
index 1844d3a1336..b6d95fd1b39 100644
--- a/cmd/cue/cmd/modedit.go
+++ b/cmd/cue/cmd/modedit.go
@@ -21,6 +21,8 @@ import (
 	"path/filepath"
 	"strconv"
 
+	"cuelang.org/go/internal/cueversion"
+	"cuelang.org/go/internal/mod/semver"
 	"cuelang.org/go/mod/modfile"
 	"cuelang.org/go/mod/module"
 	"github.com/spf13/cobra"
@@ -54,8 +56,9 @@ Note that this command is not yet stable and may be changed.
 		RunE: mkRunE(c, editCmd.run),
 		Args: cobra.ExactArgs(0),
 	}
-	addFlagVar(cmd, flagFunc(editCmd.flagSource), "source", "set the source field")
+	addFlagVar(cmd, flagFunc(editCmd.flagSource), string(flagSource), "set the source field")
 	addFlagVar(cmd, boolFlagFunc(editCmd.flagDropSource), "drop-source", "remove the source field")
+	addFlagVar(cmd, flagFunc(editCmd.flagLanguageVersion), string(flagLanguageVersion), "set language.version ('current' means current language version)")
 	addFlagVar(cmd, flagFunc(editCmd.flagModule), "module", "set the module path")
 	addFlagVar(cmd, flagFunc(editCmd.flagRequire), "require", "add a required module@version")
 	addFlagVar(cmd, flagFunc(editCmd.flagDropRequire), "drop-require", "remove a requirement")
@@ -88,7 +91,7 @@ func (c *modEditCmd) run(cmd *Command, args []string) error {
 	}
 	newData, err := mf.Format()
 	if err != nil {
-		return fmt.Errorf("internal error: invalid module.cue file generated: %v", err)
+		return fmt.Errorf("invalid resulting module.cue file after edits: %v", err)
 	}
 	if bytes.Equal(newData, data) {
 		return nil
@@ -128,6 +131,41 @@ func (c *modEditCmd) flagDropSource(arg bool) error {
 	return nil
 }
 
+func (c *modEditCmd) flagLanguageVersion(arg string) error {
+	editFunc, err := addLanguageVersion(arg)
+	if err != nil {
+		return err
+	}
+	c.addEdit(editFunc)
+	return nil
+}
+
+func addLanguageVersion(v string) (func(*modfile.File) error, error) {
+	if v == "current" {
+		v = cueversion.LanguageVersion()
+	} else {
+		if semver.Canonical(v) != v {
+			return nil, fmt.Errorf("language version %q is not canonical (must include major, minor and patch versions)", v)
+		}
+
+		if min := modfile.EarliestClosedSchemaVersion(); semver.Compare(v, min) < 0 {
+			// TODO(rogpeppe) We might want to relax this to allow people to
+			// declare an earlier language version (see https://cuelang.org/issue/3145).
+			return nil, fmt.Errorf("language version %q is too early for module.cue schema (earliest allowed is %s)", v, min)
+		}
+		if max := cueversion.LanguageVersion(); semver.Compare(v, max) > 0 {
+			return nil, fmt.Errorf("language version %q may not be after current language version %s", v, max)
+		}
+	}
+	return func(f *modfile.File) error {
+		if f.Language == nil {
+			f.Language = &modfile.Language{}
+		}
+		f.Language.Version = v
+		return nil
+	}, nil
+}
+
 func (c *modEditCmd) flagModule(arg string) error {
 	if err := module.CheckPath(arg); err != nil {
 		return err
diff --git a/cmd/cue/cmd/modinit.go b/cmd/cue/cmd/modinit.go
index fe219314389..51ad8383332 100644
--- a/cmd/cue/cmd/modinit.go
+++ b/cmd/cue/cmd/modinit.go
@@ -22,7 +22,6 @@ import (
 
 	"github.com/spf13/cobra"
 
-	"cuelang.org/go/internal/cueversion"
 	"cuelang.org/go/mod/modfile"
 	"cuelang.org/go/mod/module"
 )
@@ -45,6 +44,7 @@ in the module.
 
 	cmd.Flags().BoolP(string(flagForce), "f", false, "force moving old-style cue.mod file")
 	cmd.Flags().String(string(flagSource), "", "set the source field")
+	cmd.Flags().String(string(flagLanguageVersion), "current", "set the language version ('current' means current language version)")
 	return cmd
 }
 
@@ -84,8 +84,12 @@ func runModInit(cmd *Command, args []string) (err error) {
 			return err
 		}
 	}
-	mf.Language = &modfile.Language{
-		Version: cueversion.LanguageVersion(),
+	editFunc, err := addLanguageVersion(flagLanguageVersion.String(cmd))
+	if err != nil {
+		return err
+	}
+	if err := editFunc(mf); err != nil {
+		return err
 	}
 
 	err = os.Mkdir(mod, 0755)
diff --git a/cmd/cue/cmd/testdata/script/modedit_initial.txtar b/cmd/cue/cmd/testdata/script/modedit_initial.txtar
index 3f1d7360c43..f9536345ea4 100644
--- a/cmd/cue/cmd/testdata/script/modedit_initial.txtar
+++ b/cmd/cue/cmd/testdata/script/modedit_initial.txtar
@@ -19,6 +19,27 @@ cmp cue.mod/module.cue want-module-4
 exec cue mod edit --module othermain.org@v1
 cmp cue.mod/module.cue want-module-5
 
+# Set specific version.
+exec cue mod edit --language-version v0.9.2
+cmp cue.mod/module.cue want-module-6
+
+# Set latest version.
+exec cue mod edit --language-version current
+cmpenv cue.mod/module.cue want-module-7
+
+# Set version earlier than earliest module schema version.
+! exec cue mod edit --language-version v0.4.3
+cmp stderr want-stderr-8
+
+# Set version too new.
+! exec cue mod edit --language-version v2.3.4
+cmpenv stderr want-stderr-9
+
+# Check that it's an error to set the version earlier than
+# allowed by some of the fields already present.
+exec cue mod edit --source self
+! exec cue mod edit --language-version v0.8.0
+cmp stderr want-stderr-10
 
 -- cue.mod/module.cue --
 module: "main.org@v0"
@@ -66,3 +87,19 @@ module: "othermain.org@v1"
 language: {
 	version: "v0.9.0-alpha.0"
 }
+-- want-module-6 --
+module: "othermain.org@v1"
+language: {
+	version: "v0.9.2"
+}
+-- want-module-7 --
+module: "othermain.org@v1"
+language: {
+	version: "$CUE_LANGUAGE_VERSION"
+}
+-- want-stderr-8 --
+invalid argument "v0.4.3" for "--language-version" flag: language version "v0.4.3" is too early for module.cue schema (earliest allowed is v0.8.0-alpha.0)
+-- want-stderr-9 --
+invalid argument "v2.3.4" for "--language-version" flag: language version "v2.3.4" may not be after current language version $CUE_LANGUAGE_VERSION
+-- want-stderr-10 --
+invalid resulting module.cue file after edits: cannot parse result: invalid module.cue file: source field is not allowed at this language version; need at least v0.9.0-alpha.0
diff --git a/cmd/cue/cmd/testdata/script/modinit_with_explicit_version.txtar b/cmd/cue/cmd/testdata/script/modinit_with_explicit_version.txtar
new file mode 100644
index 00000000000..30851beae6a
--- /dev/null
+++ b/cmd/cue/cmd/testdata/script/modinit_with_explicit_version.txtar
@@ -0,0 +1,43 @@
+# Check we can initialize the module with an explicit version.
+
+# Set current version.
+exec cue mod init --language-version current foo.example
+cmpenv cue.mod/module.cue want-module-1
+rm cue.mod
+
+# Set specific version.
+exec cue mod init --language-version v0.9.2 foo.example
+cmp cue.mod/module.cue want-module-2
+rm cue.mod
+
+# Set version earlier than earliest module schema version.
+! exec cue mod init --language-version v0.4.3 foo.example
+cmp stderr want-stderr-3
+rm cue.mod
+
+# Set version too new.
+! exec cue mod init --language-version v2.3.4 foo.example
+cmp stderr want-stderr-4
+rm cue.mod
+
+# Set version that's incompatible with the source field.
+! exec cue mod init --language-version v0.8.0 --source self foo.example
+cmp stderr want-stderr-5
+rm cue.mod
+
+-- want-module-1 --
+module: "foo.example"
+language: {
+	version: "$CUE_LANGUAGE_VERSION"
+}
+-- want-module-2 --
+module: "foo.example"
+language: {
+	version: "v0.9.2"
+}
+-- want-stderr-3 --
+language version "v0.4.3" is too early for module.cue schema (earliest allowed is v0.8.0-alpha.0)
+-- want-stderr-4 --
+language version "v2.3.4" may not be after current language version v0.10.0
+-- want-stderr-5 --
+cannot parse result: invalid module.cue file: source field is not allowed at this language version; need at least v0.9.0-alpha.0
diff --git a/cmd/cue/cmd/testdata/script/modinit_without_version.txtar b/cmd/cue/cmd/testdata/script/modinit_without_version.txtar
index d4a9e36668d..a4e63ec96f1 100644
--- a/cmd/cue/cmd/testdata/script/modinit_without_version.txtar
+++ b/cmd/cue/cmd/testdata/script/modinit_without_version.txtar
@@ -1,13 +1,12 @@
 # Check that cue mod init is independent of the module version;
 # even though CUE's current module version will often be a v0 pseudo-version
 # or a pre-release, we will always use the current language version in init.
-env-fill want-module
 exec cue mod init foo.example
-cmp cue.mod/module.cue want-module
+cmpenv cue.mod/module.cue want-module
 
 # cue mod tidy should be a no-op after cue mod init
 exec cue mod tidy
-cmp cue.mod/module.cue want-module
+cmpenv cue.mod/module.cue want-module
 
 -- want-module --
 module: "foo.example"
diff --git a/mod/modfile/modfile.go b/mod/modfile/modfile.go
index 3c06a848fd6..3991af3590c 100644
--- a/mod/modfile/modfile.go
+++ b/mod/modfile/modfile.go
@@ -156,7 +156,7 @@ func (f *File) Format() ([]byte, error) {
 	// before formatting the output.
 	f1, err := ParseNonStrict(data, "-")
 	if err != nil {
-		return nil, fmt.Errorf("cannot round-trip module file: %v", strings.TrimSuffix(errors.Details(err, nil), "\n"))
+		return nil, fmt.Errorf("cannot parse result: %v", strings.TrimSuffix(errors.Details(err, nil), "\n"))
 	}
 	if f.Language != nil && f1.actualSchemaVersion == "v0.0.0" {
 		// It's not a legacy module file (because the language field is present)
@@ -363,7 +363,7 @@ func FixLegacy(modfile []byte, filename string) (*File, error) {
 	}
 	f, err = ParseNonStrict(data, "fixed-"+filename)
 	if err != nil {
-		return nil, fmt.Errorf("cannot round-trip fixed module file %q: %v", data, err)
+		return nil, fmt.Errorf("cannot parse resulting module file %q: %v", data, err)
 	}
 	return f, nil
 }
diff --git a/mod/modfile/modfile_test.go b/mod/modfile/modfile_test.go
index 6629d84e93f..9e187e488b0 100644
--- a/mod/modfile/modfile_test.go
+++ b/mod/modfile/modfile_test.go
@@ -500,7 +500,7 @@ language: {
 				Version: "v0.4.3",
 			},
 		},
-		wantError: `cannot round-trip module file: cannot find schema suitable for reading module file with language version "v0.4.3"`,
+		wantError: `cannot parse result: cannot find schema suitable for reading module file with language version "v0.4.3"`,
 	}, {
 		name: "WithInvalidModuleVersion",
 		file: &File{
@@ -509,7 +509,7 @@ language: {
 				Version: "badversion--",
 			},
 		},
-		wantError: `cannot round-trip module file: language version "badversion--" in module.cue is not valid semantic version`,
+		wantError: `cannot parse result: language version "badversion--" in module.cue is not valid semantic version`,
 	}, {
 		name: "WithNonNilEmptyDeps",
 		file: &File{