diff --git a/src/file/numbering/level.spec.ts b/src/file/numbering/level.spec.ts
index 5748a9c610..608474888a 100644
--- a/src/file/numbering/level.spec.ts
+++ b/src/file/numbering/level.spec.ts
@@ -1,5 +1,7 @@
 import { expect } from "chai";
 
+import { Formatter } from "@export/formatter";
+
 import { LevelFormat, LevelSuffix } from ".";
 import { AlignmentType } from "..";
 
@@ -22,4 +24,41 @@ describe("Level", () => {
             ).to.throw();
         });
     });
+
+    describe("isLegalNumberingStyle", () => {
+        it("should work", () => {
+            const concreteNumbering = new Level({
+                level: 9,
+                isLegalNumberingStyle: true,
+            });
+            const tree = new Formatter().format(concreteNumbering);
+            expect(tree).to.deep.equal({
+                "w:lvl": [
+                    {
+                        "w:start": {
+                            _attr: {
+                                "w:val": 1,
+                            },
+                        },
+                    },
+                    {
+                        "w:isLgl": {},
+                    },
+                    {
+                        "w:lvlJc": {
+                            _attr: {
+                                "w:val": "start",
+                            },
+                        },
+                    },
+                    {
+                        _attr: {
+                            "w15:tentative": 1,
+                            "w:ilvl": 9,
+                        },
+                    },
+                ],
+            });
+        });
+    });
 });
diff --git a/src/file/numbering/level.ts b/src/file/numbering/level.ts
index 225a1f2004..cedf0745a7 100644
--- a/src/file/numbering/level.ts
+++ b/src/file/numbering/level.ts
@@ -87,6 +87,7 @@ export interface ILevelsOptions {
     readonly alignment?: AlignmentType;
     readonly start?: number;
     readonly suffix?: LevelSuffix;
+    readonly isLegalNumberingStyle?: boolean;
     readonly style?: {
         readonly run?: IRunStylePropertiesOptions;
         readonly paragraph?: ILevelParagraphStylePropertiesOptions;
@@ -114,6 +115,14 @@ class Suffix extends XmlComponent {
     }
 }
 
+// http://officeopenxml.com/WPnumbering-isLgl.php
+// https://docs.microsoft.com/en-us/dotnet/api/documentformat.openxml.wordprocessing.islegalnumberingstyle?view=openxml-2.8.1
+class IsLegalNumberingStyle extends XmlComponent {
+    constructor() {
+        super("w:isLgl");
+    }
+}
+
 // <xsd:complexType name="CT_Lvl">
 //     <xsd:sequence>
 //         <xsd:element name="start" type="CT_DecimalNumber" minOccurs="0"/>
@@ -137,7 +146,7 @@ export class LevelBase extends XmlComponent {
     private readonly paragraphProperties: ParagraphProperties;
     private readonly runProperties: RunProperties;
 
-    constructor({ level, format, text, alignment = AlignmentType.START, start = 1, style, suffix }: ILevelsOptions) {
+    constructor({ level, format, text, alignment = AlignmentType.START, start = 1, style, suffix, isLegalNumberingStyle }: ILevelsOptions) {
         super("w:lvl");
 
         this.root.push(new NumberValueElement("w:start", decimalNumber(start)));
@@ -150,6 +159,10 @@ export class LevelBase extends XmlComponent {
             this.root.push(new Suffix(suffix));
         }
 
+        if (isLegalNumberingStyle) {
+            this.root.push(new IsLegalNumberingStyle());
+        }
+
         if (text) {
             this.root.push(new LevelText(text));
         }