diff --git a/src/tsconfig.strictNullChecks.json b/src/tsconfig.strictNullChecks.json
index f2f69af3270..2822521b941 100644
--- a/src/tsconfig.strictNullChecks.json
+++ b/src/tsconfig.strictNullChecks.json
@@ -560,6 +560,7 @@
 		"./vs/workbench/browser/part.ts",
 		"./vs/workbench/browser/parts/editor/editorWidgets.ts",
 		"./vs/workbench/browser/parts/notifications/notificationsAlerts.ts",
+		"./vs/workbench/browser/parts/quickinput/quickInputBox.ts",
 		"./vs/workbench/browser/parts/quickinput/quickInputUtils.ts",
 		"./vs/workbench/browser/parts/quickopen/quickopen.ts",
 		"./vs/workbench/browser/parts/statusbar/statusbar.ts",
@@ -742,6 +743,7 @@
 		"./vs/workbench/services/themes/common/fileIconThemeSchema.ts",
 		"./vs/workbench/services/themes/common/workbenchThemeService.ts",
 		"./vs/workbench/services/themes/electron-browser/fileIconThemeData.ts",
+		"./vs/workbench/services/themes/electron-browser/fileIconThemeStore.ts",
 		"./vs/workbench/services/title/common/titleService.ts",
 		"./vs/workbench/services/workspace/common/workspaceEditing.ts",
 		"./vs/workbench/test/electron-browser/api/mock.ts"
diff --git a/src/vs/workbench/browser/parts/quickinput/quickInputBox.ts b/src/vs/workbench/browser/parts/quickinput/quickInputBox.ts
index 0ab4759c312..bbba5345326 100644
--- a/src/vs/workbench/browser/parts/quickinput/quickInputBox.ts
+++ b/src/vs/workbench/browser/parts/quickinput/quickInputBox.ts
@@ -24,7 +24,7 @@ export class QuickInputBox {
 		private parent: HTMLElement
 	) {
 		this.container = dom.append(this.parent, $('.quick-input-box'));
-		this.inputBox = new InputBox(this.container, null);
+		this.inputBox = new InputBox(this.container, void 0);
 		this.disposables.push(this.inputBox);
 	}
 
@@ -55,7 +55,7 @@ export class QuickInputBox {
 	}
 
 	get placeholder() {
-		return this.inputBox.inputElement.getAttribute('placeholder');
+		return this.inputBox.inputElement.getAttribute('placeholder') || '';
 	}
 
 	set placeholder(placeholder: string) {
diff --git a/src/vs/workbench/services/themes/electron-browser/fileIconThemeStore.ts b/src/vs/workbench/services/themes/electron-browser/fileIconThemeStore.ts
index b2fb8c87df3..41bd8bee59e 100644
--- a/src/vs/workbench/services/themes/electron-browser/fileIconThemeStore.ts
+++ b/src/vs/workbench/services/themes/electron-browser/fileIconThemeStore.ts
@@ -105,7 +105,7 @@ export class FileIconThemeStore {
 
 	}
 
-	public findThemeData(iconTheme: string): Thenable<FileIconThemeData> {
+	public findThemeData(iconTheme: string): Thenable<FileIconThemeData | null> {
 		return this.getFileIconThemes().then(allIconSets => {
 			for (let iconSet of allIconSets) {
 				if (iconSet.id === iconTheme) {
@@ -116,7 +116,7 @@ export class FileIconThemeStore {
 		});
 	}
 
-	public findThemeBySettingsId(settingsId: string): Thenable<FileIconThemeData> {
+	public findThemeBySettingsId(settingsId: string): Thenable<FileIconThemeData | null> {
 		return this.getFileIconThemes().then(allIconSets => {
 			for (let iconSet of allIconSets) {
 				if (iconSet.settingsId === settingsId) {