diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/__snapshots__/generator.test.ts.snap b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/__snapshots__/generator.test.ts.snap
index e4d7132e65..da31fd8a63 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/__snapshots__/generator.test.ts.snap
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/__snapshots__/generator.test.ts.snap
@@ -91,6 +91,7 @@ exports[`DefaultSidebarItemsGenerator generates simple flat sidebar 1`] = `
       "custom": "prop",
     },
     "id": "doc1",
+    "key": "doc1-sidebar-key",
     "label": "doc1 sidebar label",
     "type": "doc",
   },
@@ -120,6 +121,7 @@ exports[`DefaultSidebarItemsGenerator generates subfolder sidebar 1`] = `
         "type": "doc",
       },
     ],
+    "key": "doc1-sidebar-key",
     "label": "Subsubsubfolder category label",
     "link": {
       "id": "doc1",
@@ -142,6 +144,7 @@ exports[`DefaultSidebarItemsGenerator generates subfolder sidebar 1`] = `
   },
   {
     "id": "doc1",
+    "key": "doc1-sidebar-key",
     "type": "doc",
   },
   {
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts
index 5072fd80d7..83904dd9eb 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts
@@ -63,6 +63,7 @@ describe('DefaultSidebarItemsGenerator', () => {
           sourceDirName: '.',
           sidebarPosition: 2,
           frontMatter: {
+            sidebar_key: 'doc1-sidebar-key',
             sidebar_label: 'doc1 sidebar label',
             sidebar_custom_props: {custom: 'prop'},
           },
@@ -254,7 +255,9 @@ describe('DefaultSidebarItemsGenerator', () => {
           sourceDirName: 'subfolder/subsubfolder',
           title: 'Subsubsubfolder category label',
           sidebarPosition: undefined,
-          frontMatter: {},
+          frontMatter: {
+            sidebar_key: 'doc1-sidebar-key',
+          },
         },
         {
           id: 'doc2',
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts
index 777e5b84f1..b37536c7e3 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts
@@ -147,12 +147,12 @@ Available doc IDs:
       } = getDoc(id);
       return {
         type: 'doc',
-        key,
         id,
         position,
         source: fileName,
         // We don't want these fields to magically appear in the generated
         // sidebar
+        ...(key !== undefined && {key}),
         ...(label !== undefined && {label}),
         ...(className !== undefined && {className}),
         ...(customProps !== undefined && {customProps}),