diff --git a/src/tsconfig.strictNullChecks.json b/src/tsconfig.strictNullChecks.json
index 4390a2ed85c..4f8ef3e5ecf 100644
--- a/src/tsconfig.strictNullChecks.json
+++ b/src/tsconfig.strictNullChecks.json
@@ -293,6 +293,7 @@
 		"./vs/editor/contrib/dnd/dragAndDropCommand.ts",
 		"./vs/editor/contrib/find/findDecorations.ts",
 		"./vs/editor/contrib/find/findModel.ts",
+		"./vs/editor/contrib/find/findOptionsWidget.ts",
 		"./vs/editor/contrib/find/findState.ts",
 		"./vs/editor/contrib/find/replaceAllCommand.ts",
 		"./vs/editor/contrib/find/replacePattern.ts",
diff --git a/src/vs/editor/contrib/find/findOptionsWidget.ts b/src/vs/editor/contrib/find/findOptionsWidget.ts
index 5774e2a014e..0637b0a9789 100644
--- a/src/vs/editor/contrib/find/findOptionsWidget.ts
+++ b/src/vs/editor/contrib/find/findOptionsWidget.ts
@@ -46,7 +46,7 @@ export class FindOptionsWidget extends Widget implements IOverlayWidget {
 		this._domNode.setAttribute('role', 'presentation');
 		this._domNode.setAttribute('aria-hidden', 'true');
 
-		let inputActiveOptionBorderColor = themeService.getTheme().getColor(inputActiveOptionBorder);
+		const inputActiveOptionBorderColor = themeService.getTheme().getColor(inputActiveOptionBorder) || undefined;
 
 		this.caseSensitive = this._register(new CaseSensitiveCheckbox({
 			appendTitle: this._keybindingLabelFor(FIND_IDS.ToggleCaseSensitiveCommand),
@@ -179,7 +179,7 @@ export class FindOptionsWidget extends Widget implements IOverlayWidget {
 	}
 
 	private _applyTheme(theme: ITheme) {
-		let inputStyles = { inputActiveOptionBorder: theme.getColor(inputActiveOptionBorder) };
+		let inputStyles = { inputActiveOptionBorder: theme.getColor(inputActiveOptionBorder) || undefined };
 		this.caseSensitive.style(inputStyles);
 		this.wholeWords.style(inputStyles);
 		this.regex.style(inputStyles);