diff --git a/src/cmd/go/internal/modload/list.go b/src/cmd/go/internal/modload/list.go
index 1f210b8..e8872ba 100644
--- a/src/cmd/go/internal/modload/list.go
+++ b/src/cmd/go/internal/modload/list.go
@@ -110,7 +110,13 @@
 
 	if err == nil {
 		requirements = rs
-		if !ExplicitWriteGoMod {
+		// TODO(#61605): The extra ListU clause fixes a problem with Go 1.21rc3
+		// where "go mod tidy" and "go list -m -u all" fight over whether the go.sum
+		// should be considered up-to-date. The fix for now is to always treat the
+		// go.sum as up-to-date during list -m -u. Probably the right fix is more targeted,
+		// but in general list -u is looking up other checksums in the checksum database
+		// that won't be necessary later, so it makes sense not to write the go.sum back out.
+		if !ExplicitWriteGoMod && mode&ListU == 0 {
 			err = commitRequirements(ctx, WriteOpts{})
 		}
 	}