diff --git a/csup/metadata.go b/csup/metadata.go
index 0f1adfcdf..872b8a8db 100644
--- a/csup/metadata.go
+++ b/csup/metadata.go
@@ -342,26 +342,29 @@ func metadataValue(cctx *Context, sctx *super.Context, b *scode.Builder, id ID,
 		return sctx.MustLookupTypeRecord(fields)
 	case *Union:
 		cmp := expr.NewValueCompareFn(order.Asc, order.NullsLast)
+		max, min := super.Null, super.Null
 		var bb scode.Builder
-		var min, max *super.Value
 		for _, id := range m.Values {
 			val := newMetadataValue(cctx, sctx, &bb, id, projection)
 			if val.IsNull() {
 				continue
 			}
 			min2, max2 := val.Deref("min"), val.Deref("max")
-			if min == nil || (min2 != nil && cmp(*min, *min2) > 0) {
-				min = new(min2.Copy())
+			if min2 == nil {
+				continue
+			}
+			if min.IsNull() || cmp(min, *min2) > 0 {
+				min = min2.Copy()
 			}
-			if max == nil || (max2 != nil && cmp(*max, *max2) < 0) {
-				max = new(max2.Copy())
+			if max.IsNull() || cmp(max, *max2) < 0 {
+				max = max2.Copy()
 			}
 		}
-		if min == nil {
+		if min.IsNull() {
 			b.Append(nil)
 			return super.TypeNull
 		}
-		return metadataLeaf(sctx, b, *min, *max)
+		return metadataLeaf(sctx, b, min, max)
 	case *Int:
 		return metadataLeaf(sctx, b, super.NewInt(m.Typ, m.Min), super.NewInt(m.Typ, m.Max))
 	case *Uint:
diff --git a/csup/object_test.go b/csup/object_test.go
index 5fbbfc8e1..8768d1585 100644
--- a/csup/object_test.go
+++ b/csup/object_test.go
@@ -41,8 +41,8 @@ func TestObjectProjectMetadata(t *testing.T) {
 func TestObjectProjectMetadataForUnion(t *testing.T) {
 	sctx := super.NewContext()
 	supValues := []string{
-		"{a:1::(int64|string),b?:2,c:3::(int64|null)}",
-		`{a:"s"::(int64|string),b?:_::int64,c:null::(int64|null)}`,
+		"{a:1::(int64|string),b?:2,c:3::(int64|null),d?:{e:4}}",
+		`{a:"s"::(int64|string),b?:_::int64,c:null::(int64|null),d?:_::{e:int64}}`,
 	}
 	builder := vector.NewDynamicValueBuilder()
 	for _, s := range supValues {
@@ -56,8 +56,8 @@ func TestObjectProjectMetadataForUnion(t *testing.T) {
 
 	o, err := csup.NewObject(bytes.NewReader(csupBytes))
 	require.NoError(t, err)
-	p := field.NewProjection(field.DottedList("a,b,c"))
+	p := field.NewProjection(field.DottedList("a,b,c,d"))
 	values := o.ProjectMetadata(super.NewContext(), p)
 	require.Len(t, values, 1)
-	require.Equal(t, `{a:{min:1,max:"s"},b:{min:2,max:2},c:{min:3,max:3}}`, sup.FormatValue(values[0]))
+	require.Equal(t, `{a:{min:1,max:"s"},b:{min:2,max:2},c:{min:3,max:3},d:null}`, sup.FormatValue(values[0]))
 }