diff --git a/js/docx/smoke/api_block_lvl_sdt/to_json.js b/js/docx/smoke/api_block_lvl_sdt/to_json.js
new file mode 100644
index 000000000..aadc47436
--- /dev/null
+++ b/js/docx/smoke/api_block_lvl_sdt/to_json.js
@@ -0,0 +1,38 @@
+builder.CreateFile("docx");
+    var oDocument = Api.GetDocument();
+        CustomDefaultStyle(oDocument)
+    var oBlockLvlSdt = Api.CreateBlockLvlSdt();
+        oBlockLvlSdt.SetAlias("№1");
+    var oBlockContent = oBlockLvlSdt.GetContent()
+        oBlockContent.GetElement(0).AddText("blockLvlSdt");
+    var oNumbering = oDocument.CreateNumbering("bullet");
+        for (let nLvl = 0; nLvl < 8; ++nLvl) {
+            var oNumLvl = oNumbering.GetLevel(nLvl);
+            var oParagraph = Api.CreateParagraph();
+            oParagraph.AddText("Default bullet lvl " + (nLvl + 1));
+            oParagraph.SetNumbering(oNumLvl);
+            oParagraph.SetContextualSpacing(true);
+            oBlockContent.Push(oParagraph);
+        }
+    var json = oBlockLvlSdt.ToJSON(true, true);
+        function CustomDefaultStyle(oDocument){
+            var oNormalStyle = oDocument.GetDefaultStyle("paragraph");
+            var oTextPr = oNormalStyle.GetTextPr();
+            oTextPr.SetColor(0x26, 0x26, 0x26, false);
+            oTextPr.SetFontFamily("Calibri Light");
+            oTextPr.SetFontSize(32);
+        }
+GlobalVariable["JSON"] = json;
+builder.CloseFile();
+
+////////////////////////
+
+builder.CreateFile("docx");
+    var json = GlobalVariable["JSON"];
+    var oDocument = Api.GetDocument();
+    var oParagraph = oDocument.GetElement(0);
+        oParagraph.AddText(json)
+    var oBlockSdtFromJSON = Api.FromJSON(json);
+        oDocument.AddElement(0, oBlockSdtFromJSON);
+builder.SaveFile("docx", "ToJSON.docx");
+builder.CloseFile();
diff --git a/spec/docx/smoke/api_block_lvl_sdt_spec.rb b/spec/docx/smoke/api_block_lvl_sdt_spec.rb
new file mode 100644
index 000000000..3e5d30fea
--- /dev/null
+++ b/spec/docx/smoke/api_block_lvl_sdt_spec.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'ApiBlockLvlSdt section tests' do
+  it 'ApiBlockLvlSdt | ToJSON method' do
+    docx = builder.build_and_parse('js/docx/smoke/api_block_lvl_sdt/to_json.js')
+    expect(docx.elements[0].sdt_content.elements[0].character_style_array[1].text).to eq('blockLvlSdt')
+    expect(docx.elements[0].sdt_content.elements[8].numbering.i_level.value).to eq(7)
+    json = JSON.parse(docx.elements[1].nonempty_runs.first.text)
+    expect(json['type']).to eq('blockLvlSdt')
+    expect(json['numbering']['type']).to eq('numbering')
+  end
+end