diff --git a/modfile/rule.go b/modfile/rule.go
index c6a189d..8fcf96b 100644
--- a/modfile/rule.go
+++ b/modfile/rule.go
@@ -835,11 +835,8 @@
 // AddExclude adds a exclude statement to the mod file. Errors if the provided
 // version is not a canonical version string
 func (f *File) AddExclude(path, vers string) error {
-	if !isCanonicalVersion(vers) {
-		return &module.InvalidVersionError{
-			Version: vers,
-			Err:     errors.New("must be of the form v1.2.3"),
-		}
+	if err := checkCanonicalVersion(path, vers); err != nil {
+		return err
 	}
 
 	var hint *Line
@@ -916,17 +913,15 @@
 // AddRetract adds a retract statement to the mod file. Errors if the provided
 // version interval does not consist of canonical version strings
 func (f *File) AddRetract(vi VersionInterval, rationale string) error {
-	if !isCanonicalVersion(vi.High) {
-		return &module.InvalidVersionError{
-			Version: vi.High,
-			Err:     errors.New("must be of the form v1.2.3"),
-		}
+	var path string
+	if f.Module != nil {
+		path = f.Module.Mod.Path
 	}
-	if !isCanonicalVersion(vi.Low) {
-		return &module.InvalidVersionError{
-			Version: vi.Low,
-			Err:     errors.New("must be of the form v1.2.3"),
-		}
+	if err := checkCanonicalVersion(path, vi.High); err != nil {
+		return err
+	}
+	if err := checkCanonicalVersion(path, vi.Low); err != nil {
+		return err
 	}
 
 	r := &Retract{
@@ -1086,8 +1081,40 @@
 	return semver.Compare(vii.High, vij.High) > 0
 }
 
-// isCanonicalVersion tests if the provided version string represents a valid
-// canonical version.
-func isCanonicalVersion(vers string) bool {
-	return vers != "" && semver.Canonical(vers) == vers
+// checkCanonicalVersion returns a non-nil error if vers is not a canonical
+// version string or does not match the major version of path.
+//
+// If path is non-empty, the error text suggests a format with a major version
+// corresponding to the path.
+func checkCanonicalVersion(path, vers string) error {
+	_, pathMajor, pathMajorOk := module.SplitPathVersion(path)
+
+	if vers == "" || vers != module.CanonicalVersion(vers) {
+		if pathMajor == "" {
+			return &module.InvalidVersionError{
+				Version: vers,
+				Err:     fmt.Errorf("must be of the form v1.2.3"),
+			}
+		}
+		return &module.InvalidVersionError{
+			Version: vers,
+			Err:     fmt.Errorf("must be of the form %s.2.3", module.PathMajorPrefix(pathMajor)),
+		}
+	}
+
+	if pathMajorOk {
+		if err := module.CheckPathMajor(vers, pathMajor); err != nil {
+			if pathMajor == "" {
+				// In this context, the user probably wrote "v2.3.4" when they meant
+				// "v2.3.4+incompatible". Suggest that instead of "v0 or v1".
+				return &module.InvalidVersionError{
+					Version: vers,
+					Err:     fmt.Errorf("should be %s+incompatible (or module %s/%v)", vers, path, semver.Major(vers)),
+				}
+			}
+			return err
+		}
+	}
+
+	return nil
 }
diff --git a/modfile/rule_test.go b/modfile/rule_test.go
index 03123ed..2381ee6 100644
--- a/modfile/rule_test.go
+++ b/modfile/rule_test.go
@@ -6,6 +6,7 @@
 
 import (
 	"bytes"
+	"fmt"
 	"testing"
 
 	"golang.org/x/mod/module"
@@ -189,6 +190,45 @@
 	},
 }
 
+var addExcludeTests = []struct {
+	desc    string
+	in      string
+	path    string
+	version string
+	out     string
+}{
+	{
+		`compatible`,
+		`module m
+		`,
+		`example.com`,
+		`v1.2.3`,
+		`module m
+		exclude example.com v1.2.3
+		`,
+	},
+	{
+		`gopkg.in v0`,
+		`module m
+		`,
+		`gopkg.in/foo.v0`,
+		`v0.2.3`,
+		`module m
+		exclude gopkg.in/foo.v0 v0.2.3
+		`,
+	},
+	{
+		`gopkg.in v1`,
+		`module m
+		`,
+		`gopkg.in/foo.v1`,
+		`v1.2.3`,
+		`module m
+		exclude gopkg.in/foo.v1 v1.2.3
+		`,
+	},
+}
+
 var addRetractTests = []struct {
 	desc      string
 	in        string
@@ -569,44 +609,90 @@
 }
 
 var addRetractValidateVersionTests = []struct {
-	dsc, low, high string
+	desc      string
+	path      string
+	low, high string
+	wantErr   string
 }{
 	{
-		"blank_version",
-		"",
-		"",
+		`blank_version`,
+		`example.com/m`,
+		``,
+		``,
+		`version "" invalid: must be of the form v1.2.3`,
 	},
 	{
-		"missing_prefix",
-		"1.0.0",
-		"1.0.0",
+		`missing prefix`,
+		`example.com/m`,
+		`1.0.0`,
+		`1.0.0`,
+		`version "1.0.0" invalid: must be of the form v1.2.3`,
 	},
 	{
-		"non_canonical",
-		"v1.2",
-		"v1.2",
+		`non-canonical`,
+		`example.com/m`,
+		`v1.2`,
+		`v1.2`,
+		`version "v1.2" invalid: must be of the form v1.2.3`,
 	},
 	{
-		"invalid_range",
-		"v1.2.3",
-		"v1.3",
+		`invalid range`,
+		`example.com/m`,
+		`v1.2.3`,
+		`v1.3`,
+		`version "v1.3" invalid: must be of the form v1.2.3`,
+	},
+	{
+		`mismatched major`,
+		`example.com/m/v2`,
+		`v1.0.0`,
+		`v1.0.0`,
+		`version "v1.0.0" invalid: should be v2, not v1`,
+	},
+	{
+		`missing +incompatible`,
+		`example.com/m`,
+		`v2.0.0`,
+		`v2.0.0`,
+		`version "v2.0.0" invalid: should be v2.0.0+incompatible (or module example.com/m/v2)`,
 	},
 }
 
 var addExcludeValidateVersionTests = []struct {
-	dsc, ver string
+	desc    string
+	path    string
+	version string
+	wantErr string
 }{
 	{
-		"blank_version",
-		"",
+		`blank version`,
+		`example.com/m`,
+		``,
+		`version "" invalid: must be of the form v1.2.3`,
 	},
 	{
-		"missing_prefix",
-		"1.0.0",
+		`missing prefix`,
+		`example.com/m`,
+		`1.0.0`,
+		`version "1.0.0" invalid: must be of the form v1.2.3`,
 	},
 	{
-		"non_canonical",
-		"v1.2",
+		`non-canonical`,
+		`example.com/m`,
+		`v1.2`,
+		`version "v1.2" invalid: must be of the form v1.2.3`,
+	},
+	{
+		`mismatched major`,
+		`example.com/m/v2`,
+		`v1.2.3`,
+		`version "v1.2.3" invalid: should be v2, not v1`,
+	},
+	{
+		`missing +incompatible`,
+		`example.com/m`,
+		`v2.3.4`,
+		`version "v2.3.4" invalid: should be v2.3.4+incompatible (or module example.com/m/v2)`,
 	},
 }
 
@@ -657,6 +743,16 @@
 	}
 }
 
+func TestAddExclude(t *testing.T) {
+	for _, tt := range addExcludeTests {
+		t.Run(tt.desc, func(t *testing.T) {
+			testEdit(t, tt.in, tt.out, true, func(f *File) error {
+				return f.AddExclude(tt.path, tt.version)
+			})
+		})
+	}
+}
+
 func TestAddRetract(t *testing.T) {
 	for _, tt := range addRetractTests {
 		t.Run(tt.desc, func(t *testing.T) {
@@ -744,13 +840,21 @@
 
 func TestAddRetractValidateVersion(t *testing.T) {
 	for _, tt := range addRetractValidateVersionTests {
-		t.Run(tt.dsc, func(t *testing.T) {
-			f, err := Parse("in", []byte("module m"), nil)
-			if err != nil {
-				t.Fatal(err)
+		t.Run(tt.desc, func(t *testing.T) {
+			f := new(File)
+			if tt.path != "" {
+				if err := f.AddModuleStmt(tt.path); err != nil {
+					t.Fatal(err)
+				}
+				t.Logf("module %s", AutoQuote(tt.path))
 			}
-			if err = f.AddRetract(VersionInterval{Low: tt.low, High: tt.high}, ""); err == nil {
-				t.Fatal("expected AddRetract to complain about version format")
+			interval := VersionInterval{Low: tt.low, High: tt.high}
+			if err := f.AddRetract(interval, ``); err == nil || err.Error() != tt.wantErr {
+				errStr := "<nil>"
+				if err != nil {
+					errStr = fmt.Sprintf("%#q", err)
+				}
+				t.Fatalf("f.AddRetract(%+v, ``) = %s\nwant %#q", interval, errStr, tt.wantErr)
 			}
 		})
 	}
@@ -758,13 +862,17 @@
 
 func TestAddExcludeValidateVersion(t *testing.T) {
 	for _, tt := range addExcludeValidateVersionTests {
-		t.Run(tt.dsc, func(t *testing.T) {
+		t.Run(tt.desc, func(t *testing.T) {
 			f, err := Parse("in", []byte("module m"), nil)
 			if err != nil {
 				t.Fatal(err)
 			}
-			if err = f.AddExclude("aa", tt.ver); err == nil {
-				t.Fatal("expected AddExclude to complain about version format")
+			if err = f.AddExclude(tt.path, tt.version); err == nil || err.Error() != tt.wantErr {
+				errStr := "<nil>"
+				if err != nil {
+					errStr = fmt.Sprintf("%#q", err)
+				}
+				t.Fatalf("f.AddExclude(%q, %q) = %s\nwant %#q", tt.path, tt.version, errStr, tt.wantErr)
 			}
 		})
 	}