diff --git a/libs/core/src/lib/declarations/known-keys.d.ts b/libs/core/src/lib/declarations/known-keys.d.ts
new file mode 100644
index 00000000..ced16ee5
--- /dev/null
+++ b/libs/core/src/lib/declarations/known-keys.d.ts
@@ -0,0 +1,22 @@
+/**
+ * Get the known keys (i.e. no index signature) of T.
+ *
+ * @example
+```typescript
+interface Options {
+  key: string;
+  title: string;
+  [dataProperty: string]: string | number;
+}
+
+type KnownKeysOfOptions = KnownKeys<Options>; // 'key' | 'title';
+// (vs. type KeysOfOptions = keyof Options // string | number;)
+```
+
+ * Taken from https://stackoverflow.com/questions/51465182/typescript-remove-index-signature-using-mapped-types
+ */
+export type KnownKeys<T> = { [K in keyof T]: string extends K ? never : number extends K ? never : K } extends {
+  [_ in keyof T]: infer U
+}
+  ? U
+  : never;
diff --git a/libs/core/src/lib/declarations/omit.d.ts b/libs/core/src/lib/declarations/omit.d.ts
index 8a7a8923..1affee35 100644
--- a/libs/core/src/lib/declarations/omit.d.ts
+++ b/libs/core/src/lib/declarations/omit.d.ts
@@ -1,4 +1,6 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
-export type Omit<T, K extends keyof T> = Pick<T, Exclude<keyof T, K>>;
+import { KnownKeys } from './known-keys';
+
+export type Omit<T, K extends keyof T> = Pick<T, Exclude<KnownKeys<T> & keyof T, K>>;
diff --git a/libs/core/src/lib/declarations/public-api.d.ts b/libs/core/src/lib/declarations/public-api.d.ts
index 887206a2..11137158 100644
--- a/libs/core/src/lib/declarations/public-api.d.ts
+++ b/libs/core/src/lib/declarations/public-api.d.ts
@@ -1,5 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
+export * from './index-signature';
+export * from './known-keys';
 export * from './omit';
 export * from './StringMap';
diff --git a/libs/fabric/src/lib/components/command-bar/command-bar.component.ts b/libs/fabric/src/lib/components/command-bar/command-bar.component.ts
index bcef9d15..d3d276c9 100644
--- a/libs/fabric/src/lib/components/command-bar/command-bar.component.ts
+++ b/libs/fabric/src/lib/components/command-bar/command-bar.component.ts
@@ -2,7 +2,21 @@
 // Licensed under the MIT License.
 
 import { InputRendererOptions, Omit, ReactWrapperComponent } from '@angular-react/core';
-import { AfterContentInit, ChangeDetectionStrategy, ChangeDetectorRef, Component, ContentChild, ElementRef, EventEmitter, Input, OnDestroy, Output, QueryList, Renderer2, ViewChild } from '@angular/core';
+import {
+  AfterContentInit,
+  ChangeDetectionStrategy,
+  ChangeDetectorRef,
+  Component,
+  ContentChild,
+  ElementRef,
+  EventEmitter,
+  Input,
+  OnDestroy,
+  Output,
+  QueryList,
+  Renderer2,
+  ViewChild,
+} from '@angular/core';
 import { ICommandBarItemProps, ICommandBarProps } from 'office-ui-fabric-react/lib/CommandBar';
 import { IContextualMenuItem } from 'office-ui-fabric-react/lib/ContextualMenu';
 import { Subscription } from 'rxjs';
@@ -10,7 +24,12 @@ import { OnChanges, TypedChanges } from '../../declarations/angular/typed-change
 import omit from '../../utils/omit';
 import { mergeItemChanges } from '../core/declarative/item-changed';
 import { CommandBarItemChangedPayload, CommandBarItemDirective } from './directives/command-bar-item.directives';
-import { CommandBarFarItemsDirective, CommandBarItemsDirective, CommandBarItemsDirectiveBase, CommandBarOverflowItemsDirective } from './directives/command-bar-items.directives';
+import {
+  CommandBarFarItemsDirective,
+  CommandBarItemsDirective,
+  CommandBarItemsDirectiveBase,
+  CommandBarOverflowItemsDirective,
+} from './directives/command-bar-items.directives';
 
 @Component({
   selector: 'fab-command-bar',
@@ -195,9 +214,10 @@ export class FabCommandBarComponent extends ReactWrapperComponent<ICommandBarPro
     return Object.assign(
       {},
       sharedProperties,
-      iconRenderer && {
-        onRenderIcon: (item: IContextualMenuItem) => iconRenderer({ contextualMenuItem: item }),
-      } as any /* NOTE: Fix for wrong typings of `onRenderIcon` in office-ui-fabric-react */,
+      iconRenderer &&
+        ({
+          onRenderIcon: (item: IContextualMenuItem) => iconRenderer({ contextualMenuItem: item }),
+        } as any) /* NOTE: Fix for wrong typings of `onRenderIcon` in office-ui-fabric-react */,
       renderer &&
         ({ onRender: (item, dismissMenu) => renderer({ item, dismissMenu }) } as Pick<ICommandBarItemProps, 'onRender'>)
     ) as ICommandBarItemProps;
@@ -205,7 +225,6 @@ export class FabCommandBarComponent extends ReactWrapperComponent<ICommandBarPro
 }
 
 export interface ICommandBarItemOptions<TData = any> extends Omit<ICommandBarItemProps, 'onRender' | 'onRenderIcon'> {
-  readonly [propertyName: string]: any;
   readonly renderIcon?: InputRendererOptions<ICommandBarItemOptionsRenderIconContext>;
   readonly render?: InputRendererOptions<ICommandBarItemOptionsRenderContext>;
   readonly data?: TData;
diff --git a/tsconfig.json b/tsconfig.json
index 5d1aa609..c8ba5d27 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -10,6 +10,7 @@
     "typeRoots": ["node_modules/@types"],
     "lib": ["es2017", "dom"],
     "baseUrl": ".",
+    "skipLibCheck": true,
     "paths": {
       "@angular-react/*": ["libs/*"],
       "@angular-react/core": ["libs/core/src/index.ts"],