diff --git a/packages/mdc-top-app-bar/fixed/foundation.ts b/packages/mdc-top-app-bar/fixed/foundation.ts
index cb3127bf977..78e2bbb60f0 100644
--- a/packages/mdc-top-app-bar/fixed/foundation.ts
+++ b/packages/mdc-top-app-bar/fixed/foundation.ts
@@ -32,7 +32,7 @@ class MDCFixedTopAppBarFoundation extends MDCTopAppBarFoundation {
   private wasScrolled_ = false;
 
   /* istanbul ignore next */
-  constructor(adapter: Partial<MDCTopAppBarAdapter> = {}) {
+  constructor(adapter?: Partial<MDCTopAppBarAdapter>) {
     super(adapter);
 
     this.scrollHandler_ = () => this.fixedScrollHandler_();
diff --git a/packages/mdc-top-app-bar/foundation.ts b/packages/mdc-top-app-bar/foundation.ts
index c62c844aa3a..0c7c2de809e 100644
--- a/packages/mdc-top-app-bar/foundation.ts
+++ b/packages/mdc-top-app-bar/foundation.ts
@@ -68,7 +68,7 @@ class MDCTopAppBarBaseFoundation extends MDCFoundation<MDCTopAppBarAdapter> {
   private readonly navClickHandler_: EventListener;
 
   /* istanbul ignore next */
-  constructor(adapter: Partial<MDCTopAppBarAdapter> = {}) {
+  constructor(adapter?: Partial<MDCTopAppBarAdapter>) {
     super({...MDCTopAppBarBaseFoundation.defaultAdapter, ...adapter});
 
     this.navClickHandler_ = () => this.adapter_.notifyNavigationIconClicked();
diff --git a/packages/mdc-top-app-bar/short/foundation.ts b/packages/mdc-top-app-bar/short/foundation.ts
index 2e6906e6591..a49316bc709 100644
--- a/packages/mdc-top-app-bar/short/foundation.ts
+++ b/packages/mdc-top-app-bar/short/foundation.ts
@@ -32,7 +32,7 @@ class MDCShortTopAppBarFoundation extends MDCTopAppBarBaseFoundation {
   isCollapsed = false;
 
   /* istanbul ignore next */
-  constructor(adapter: Partial<MDCTopAppBarAdapter> = {}) {
+  constructor(adapter?: Partial<MDCTopAppBarAdapter>) {
     super(adapter);
   }
 
diff --git a/packages/mdc-top-app-bar/standard/foundation.ts b/packages/mdc-top-app-bar/standard/foundation.ts
index 8b2aced3d94..f8c18990804 100644
--- a/packages/mdc-top-app-bar/standard/foundation.ts
+++ b/packages/mdc-top-app-bar/standard/foundation.ts
@@ -69,7 +69,7 @@ class MDCTopAppBarFoundation extends MDCTopAppBarBaseFoundation {
   private resizeDebounceId_ = INITIAL_VALUE;
 
   /* istanbul ignore next */
-  constructor(adapter: Partial<MDCTopAppBarAdapter> = {}) {
+  constructor(adapter?: Partial<MDCTopAppBarAdapter>) {
     super(adapter);
 
     this.lastScrollPosition_ = this.adapter_.getViewportScrollY();