diff --git a/internal/plans/objchange/plan_valid.go b/internal/plans/objchange/plan_valid.go
index c20241267b..5e9ac2a832 100644
--- a/internal/plans/objchange/plan_valid.go
+++ b/internal/plans/objchange/plan_valid.go
@@ -447,14 +447,10 @@ func assertPlannedObjectValid(schema *configschema.Object, prior, config, planne
 		}
 
 	case configschema.NestingSet:
-		if !planned.IsKnown() || !config.IsKnown() {
-			// if either is unknown we cannot check the lengths
-			return errs
-		}
+		plannedL := planned.Length()
+		configL := config.Length()
 
-		plannedL := planned.LengthInt()
-		configL := config.LengthInt()
-		if plannedL != configL {
+		if ok := plannedL.Range().Includes(configL); ok.IsKnown() && ok.False() {
 			errs = append(errs, path.NewErrorf("count in plan (%#v) disagrees with count in config (%#v)", plannedL, configL))
 			return errs
 		}
diff --git a/internal/plans/objchange/plan_valid_test.go b/internal/plans/objchange/plan_valid_test.go
index 56fb4cfa81..2b1a502f63 100644
--- a/internal/plans/objchange/plan_valid_test.go
+++ b/internal/plans/objchange/plan_valid_test.go
@@ -1700,7 +1700,7 @@ func TestAssertPlanValid(t *testing.T) {
 			&configschema.Block{
 				Attributes: map[string]*configschema.Attribute{
 					"set": {
-						//Computed: true,
+						Computed: true,
 						Optional: true,
 						NestedType: &configschema.Object{
 							Nesting: configschema.NestingSet,