diff --git a/src/cmd/go/internal/modfile/rule.go b/src/cmd/go/internal/modfile/rule.go
index e1f2687..1b64216 100644
--- a/src/cmd/go/internal/modfile/rule.go
+++ b/src/cmd/go/internal/modfile/rule.go
@@ -566,6 +566,9 @@
 				var newLines []*Line
 				for _, line := range stmt.Line {
 					if p, err := parseString(&line.Token[0]); err == nil && need[p] != "" {
+						if len(line.Comments.Before) == 1 && len(line.Comments.Before[0].Token) == 0 {
+							line.Comments.Before = line.Comments.Before[:0]
+						}
 						line.Token[1] = need[p]
 						delete(need, p)
 						setIndirect(line, indirect[p])
diff --git a/src/cmd/go/internal/modfile/rule_test.go b/src/cmd/go/internal/modfile/rule_test.go
index b88ad62..edd2890 100644
--- a/src/cmd/go/internal/modfile/rule_test.go
+++ b/src/cmd/go/internal/modfile/rule_test.go
@@ -8,6 +8,8 @@
 	"bytes"
 	"fmt"
 	"testing"
+
+	"cmd/go/internal/module"
 )
 
 var addRequireTests = []struct {
@@ -59,6 +61,40 @@
 	},
 }
 
+var setRequireTests = []struct {
+	in   string
+	mods []struct {
+		path string
+		vers string
+	}
+	out string
+}{
+	{
+		`module m
+		require (
+			x.y/b v1.2.3
+
+			x.y/a v1.2.3
+		)
+		`,
+		[]struct {
+			path string
+			vers string
+		}{
+			{"x.y/a", "v1.2.3"},
+			{"x.y/b", "v1.2.3"},
+			{"x.y/c", "v1.2.3"},
+		},
+		`module m
+		require (
+			x.y/a v1.2.3
+			x.y/b v1.2.3
+			x.y/c v1.2.3
+		)
+		`,
+	},
+}
+
 func TestAddRequire(t *testing.T) {
 	for i, tt := range addRequireTests {
 		t.Run(fmt.Sprintf("#%d", i), func(t *testing.T) {
@@ -88,3 +124,40 @@
 		})
 	}
 }
+
+func TestSetRequire(t *testing.T) {
+	for i, tt := range setRequireTests {
+		t.Run(fmt.Sprintf("#%d", i), func(t *testing.T) {
+			f, err := Parse("in", []byte(tt.in), nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			g, err := Parse("out", []byte(tt.out), nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			golden, err := g.Format()
+			if err != nil {
+				t.Fatal(err)
+			}
+			var mods []*Require
+			for _, mod := range tt.mods {
+				mods = append(mods, &Require{
+					Mod: module.Version{
+						Path:    mod.path,
+						Version: mod.vers,
+					},
+				})
+			}
+
+			f.SetRequire(mods)
+			out, err := f.Format()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !bytes.Equal(out, golden) {
+				t.Errorf("have:\n%s\nwant:\n%s", out, golden)
+			}
+		})
+	}
+}