diff --git a/src/cmd/go/internal/mvs/mvs.go b/src/cmd/go/internal/mvs/mvs.go
index b630b610f10..f016d8ff15d 100644
--- a/src/cmd/go/internal/mvs/mvs.go
+++ b/src/cmd/go/internal/mvs/mvs.go
@@ -293,10 +293,15 @@ func Req(target module.Version, base []string, reqs Reqs) ([]module.Version, err
 	}
 	// First walk the base modules that must be listed.
 	var min []module.Version
+	haveBase := map[string]bool{}
 	for _, path := range base {
+		if haveBase[path] {
+			continue
+		}
 		m := module.Version{Path: path, Version: max[path]}
 		min = append(min, m)
 		walk(m)
+		haveBase[path] = true
 	}
 	// Now the reverse postorder to bring in anything else.
 	for i := len(postorder) - 1; i >= 0; i-- {
diff --git a/src/cmd/go/internal/mvs/mvs_test.go b/src/cmd/go/internal/mvs/mvs_test.go
index 721cd9635c8..995a38fa92a 100644
--- a/src/cmd/go/internal/mvs/mvs_test.go
+++ b/src/cmd/go/internal/mvs/mvs_test.go
@@ -327,6 +327,19 @@ B1: Cnone D1
 E1: Fnone
 build M: M B1 D1 E1
 req M: B1 E1
+
+name: reqdup
+M: A1 B1
+A1: B1
+B1:
+req M A A: A1
+
+name: reqcross
+M: A1 B1 C1
+A1: B1 C1
+B1: C1
+C1:
+req M A B: A1 B1
 `
 
 func Test(t *testing.T) {