diff --git a/internal/topdata/convert.go b/internal/topdata/convert.go
index ef47bad..d2ce37a 100644
--- a/internal/topdata/convert.go
+++ b/internal/topdata/convert.go
@@ -876,7 +876,7 @@ func write2DAFile(data parsed2DA, path string) error {
 	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil && filepath.Dir(path) != "." {
 		return err
 	}
-	return write2DA(table, path, false)
+	return write2DA(table, path, false, -1)
 }
 
 func cloneStringMap(in map[string]string) map[string]string {
diff --git a/internal/topdata/generated_assets.go b/internal/topdata/generated_assets.go
index a8ad32c..e0591ab 100644
--- a/internal/topdata/generated_assets.go
+++ b/internal/topdata/generated_assets.go
@@ -106,7 +106,7 @@ func buildGenerated2DAAssetGroup(p *project.Project, cfg project.GeneratedTopDat
 		outputPath := filepath.Join(outputDir, dataset.Dataset.OutputName)
 		denseRows := dataset.Dataset.Kind == nativeDatasetBase ||
 			(consumer.Mode == "parts_rows" && isPartsDataset(dataset.Dataset.Name))
-		if err := write2DA(compiled, outputPath, denseRows); err != nil {
+		if err := write2DA(compiled, outputPath, denseRows, -1); err != nil {
 			return nil, err
 		}
 		results = append(results, Generated2DAAsset{
diff --git a/internal/topdata/native.go b/internal/topdata/native.go
index 2dbe1e8..054bd75 100644
--- a/internal/topdata/native.go
+++ b/internal/topdata/native.go
@@ -48,6 +48,7 @@ type nativeCollectedDataset struct {
 	LockData     map[string]int
 	RetiredKeys  map[string]struct{}
 	TableKey     string
+	DenseRowMax  int
 	LockAdded    int
 	LockPruned   int
 	LockModified bool
@@ -370,7 +371,7 @@ func buildNativeUnchecked(p *project.Project, opts NativeBuildOptions, progress
 		if err != nil {
 			return BuildResult{}, err
 		}
-		if err := write2DA(compiled, filepath.Join(output2DA, dataset.Dataset.OutputName), dataset.Dataset.Kind == nativeDatasetBase); err != nil {
+		if err := write2DA(compiled, filepath.Join(output2DA, dataset.Dataset.OutputName), dataset.Dataset.Kind == nativeDatasetBase, dataset.DenseRowMax); err != nil {
 			return BuildResult{}, err
 		}
 	}
@@ -1228,6 +1229,7 @@ func collectBaseDataset(dataset nativeDataset) (nativeCollectedDataset, error) {
 		Rows:         rows,
 		LockData:     lockData,
 		RetiredKeys:  retiredKeys,
+		DenseRowMax:  baseBoundaryID,
 		LockAdded:    lockAdded,
 		LockPruned:   lockPruned,
 		LockModified: lockModified,
@@ -5181,7 +5183,7 @@ func normalizeCollectedSpellImpactScripts(rows []map[string]any, baseRowKeys map
 	}
 }
 
-func write2DA(data map[string]any, path string, denseRows bool) error {
+func write2DA(data map[string]any, path string, denseRows bool, denseRowMax int) error {
 	columns, ok := data["columns"].([]string)
 	if !ok {
 		return fmt.Errorf("2da columns must be []string")
@@ -5223,6 +5225,17 @@ func write2DA(data map[string]any, path string, denseRows bool) error {
 			nextID = rowID + 1
 		}
 	}
+	if denseRows {
+		for nextID <= denseRowMax {
+			builder.WriteString(strconv.Itoa(nextID))
+			for range columns {
+				builder.WriteByte('\t')
+				builder.WriteString(nullValue)
+			}
+			builder.WriteByte('\n')
+			nextID++
+		}
+	}
 	return os.WriteFile(path, []byte(builder.String()), 0o644)
 }
 
diff --git a/internal/topdata/topdata_test.go b/internal/topdata/topdata_test.go
index 2245141..d26329f 100644
--- a/internal/topdata/topdata_test.go
+++ b/internal/topdata/topdata_test.go
@@ -657,14 +657,16 @@ func TestBuildNativeAllocatesConfiguredDatasetsIntoFirstNullBaseRows(t *testing.
     {"id": 0, "key": "portraits:none", "BaseResRef": "****", "Sex": 4},
     {"id": 1, "BaseResRef": "****", "Sex": "****"},
     {"id": 2, "BaseResRef": null, "Sex": null},
-    {"id": 3, "key": "portraits:existing", "BaseResRef": "existing_", "Sex": 1}
+    {"id": 3, "key": "portraits:existing", "BaseResRef": "existing_", "Sex": 1},
+    {"id": 4, "BaseResRef": "****", "Sex": "****"},
+    {"id": 5, "BaseResRef": "****", "Sex": "****"}
   ]
 }`+"\n")
 	writeFile(t, filepath.Join(root, "topdata", "data", "portraits", "lock.json"), `{
   "portraits:none": 0,
   "portraits:existing": 3,
-  "portraits:first": 4,
-  "portraits:second": 5
+  "portraits:first": 6,
+  "portraits:second": 7
 }`+"\n")
 	writeFile(t, filepath.Join(root, "topdata", "data", "portraits", "modules", "custom.json"), `{
   "entries": {
@@ -698,6 +700,8 @@ func TestBuildNativeAllocatesConfiguredDatasetsIntoFirstNullBaseRows(t *testing.
 	for _, want := range []string{
 		"1\tfirst_\t4",
 		"2\tsecond_\t4",
+		"4\t****\t****",
+		"5\t****\t****",
 	} {
 		if !strings.Contains(output, want) {
 			t.Fatalf("expected generated portraits row %q, got:\n%s", want, output)