diff --git a/src/tsconfig.strictNullChecks.json b/src/tsconfig.strictNullChecks.json
index 4bce8607d066793de65568c1bf886485e523a9df..4390a2ed85c124da023e81ee50ed0afc1a53bacc 100644
--- a/src/tsconfig.strictNullChecks.json
+++ b/src/tsconfig.strictNullChecks.json
@@ -31,6 +31,7 @@
 		"./vs/base/browser/ui/checkbox/checkbox.ts",
 		"./vs/base/browser/ui/contextview/contextview.ts",
 		"./vs/base/browser/ui/countBadge/countBadge.ts",
+		"./vs/base/browser/ui/findinput/findInput.ts",
 		"./vs/base/browser/ui/findinput/findInputCheckboxes.ts",
 		"./vs/base/browser/ui/grid/grid.ts",
 		"./vs/base/browser/ui/grid/gridview.ts",
diff --git a/src/vs/base/browser/ui/findinput/findInput.ts b/src/vs/base/browser/ui/findinput/findInput.ts
index df0567032a31c76963c4a6648c5f13b0814b8fd6..737c69da3b482a1b9899df31507fb3ecc7328e9c 100644
--- a/src/vs/base/browser/ui/findinput/findInput.ts
+++ b/src/vs/base/browser/ui/findinput/findInput.ts
@@ -44,24 +44,24 @@ export class FindInput extends Widget {
 	private contextViewProvider: IContextViewProvider;
 	private width: number;
 	private placeholder: string;
-	private validation: IInputValidator;
+	private validation?: IInputValidator;
 	private label: string;
 	private fixFocusOnOptionClickEnabled = true;
 
-	private inputActiveOptionBorder: Color;
-	private inputBackground: Color;
-	private inputForeground: Color;
-	private inputBorder: Color;
-
-	private inputValidationInfoBorder: Color;
-	private inputValidationInfoBackground: Color;
-	private inputValidationInfoForeground: Color;
-	private inputValidationWarningBorder: Color;
-	private inputValidationWarningBackground: Color;
-	private inputValidationWarningForeground: Color;
-	private inputValidationErrorBorder: Color;
-	private inputValidationErrorBackground: Color;
-	private inputValidationErrorForeground: Color;
+	private inputActiveOptionBorder?: Color;
+	private inputBackground?: Color;
+	private inputForeground?: Color;
+	private inputBorder?: Color;
+
+	private inputValidationInfoBorder?: Color;
+	private inputValidationInfoBackground?: Color;
+	private inputValidationInfoForeground?: Color;
+	private inputValidationWarningBorder?: Color;
+	private inputValidationWarningBackground?: Color;
+	private inputValidationWarningForeground?: Color;
+	private inputValidationErrorBorder?: Color;
+	private inputValidationErrorBackground?: Color;
+	private inputValidationErrorForeground?: Color;
 
 	private regex: RegexCheckbox;
 	private wholeWords: WholeWordsCheckbox;
@@ -90,7 +90,7 @@ export class FindInput extends Widget {
 	private _onRegexKeyDown = this._register(new Emitter<IKeyboardEvent>());
 	public readonly onRegexKeyDown: Event<IKeyboardEvent> = this._onRegexKeyDown.event;
 
-	constructor(parent: HTMLElement, contextViewProvider: IContextViewProvider, private readonly _showOptionButtons: boolean, options?: IFindInputOptions) {
+	constructor(parent: HTMLElement, contextViewProvider: IContextViewProvider, private readonly _showOptionButtons: boolean, options: IFindInputOptions) {
 		super();
 		this.contextViewProvider = contextViewProvider;
 		this.width = options.width || 100;
@@ -113,13 +113,7 @@ export class FindInput extends Widget {
 		this.inputValidationErrorBackground = options.inputValidationErrorBackground;
 		this.inputValidationErrorForeground = options.inputValidationErrorForeground;
 
-		this.regex = null;
-		this.wholeWords = null;
-		this.caseSensitive = null;
-		this.domNode = null;
-		this.inputBox = null;
-
-		this.buildDomNode(options.appendCaseSensitiveLabel || '', options.appendWholeWordsLabel || '', options.appendRegexLabel || '', options.history, options.flexibleHeight);
+		this.buildDomNode(options.appendCaseSensitiveLabel || '', options.appendWholeWordsLabel || '', options.appendRegexLabel || '', options.history || [], !!options.flexibleHeight);
 
 		if (Boolean(parent)) {
 			parent.appendChild(this.domNode);
@@ -298,7 +292,7 @@ export class FindInput extends Widget {
 			placeholder: this.placeholder || '',
 			ariaLabel: this.label || '',
 			validationOptions: {
-				validation: this.validation || null
+				validation: this.validation
 			},
 			inputBackground: this.inputBackground,
 			inputForeground: this.inputForeground,
@@ -370,7 +364,7 @@ export class FindInput extends Widget {
 			if (event.equals(KeyCode.LeftArrow) || event.equals(KeyCode.RightArrow) || event.equals(KeyCode.Escape)) {
 				let index = indexes.indexOf(<HTMLElement>document.activeElement);
 				if (index >= 0) {
-					let newIndex: number;
+					let newIndex: number = -1;
 					if (event.equals(KeyCode.RightArrow)) {
 						newIndex = (index + 1) % indexes.length;
 					} else if (event.equals(KeyCode.LeftArrow)) {
@@ -405,19 +399,27 @@ export class FindInput extends Widget {
 	}
 
 	public validate(): void {
-		this.inputBox.validate();
+		if (this.inputBox) {
+			this.inputBox.validate();
+		}
 	}
 
 	public showMessage(message: InputBoxMessage): void {
-		this.inputBox.showMessage(message);
+		if (this.inputBox) {
+			this.inputBox.showMessage(message);
+		}
 	}
 
 	public clearMessage(): void {
-		this.inputBox.hideMessage();
+		if (this.inputBox) {
+			this.inputBox.hideMessage();
+		}
 	}
 
 	private clearValidation(): void {
-		this.inputBox.hideMessage();
+		if (this.inputBox) {
+			this.inputBox.hideMessage();
+		}
 	}
 
 	public dispose(): void {
diff --git a/src/vs/base/browser/ui/inputbox/inputBox.ts b/src/vs/base/browser/ui/inputbox/inputBox.ts
index 055e5bfb59d613a12f090570e3da80f88238d37b..49e86d2226e972e55591b75bfa1f8f4df1bfe4ff 100644
--- a/src/vs/base/browser/ui/inputbox/inputBox.ts
+++ b/src/vs/base/browser/ui/inputbox/inputBox.ts
@@ -57,7 +57,7 @@ export interface IMessage {
 }
 
 export interface IInputValidationOptions {
-	validation: IInputValidator;
+	validation?: IInputValidator;
 }
 
 export const enum MessageType {