diff --git a/libs/cdk/coalescing/src/lib/coalesceWith.ts b/libs/cdk/coalescing/src/lib/coalesceWith.ts
index b1c99f4a34..8e7508a455 100644
--- a/libs/cdk/coalescing/src/lib/coalesceWith.ts
+++ b/libs/cdk/coalescing/src/lib/coalesceWith.ts
@@ -59,7 +59,7 @@ export function coalesceWith<T>(
       outerObserver: Subscriber<T>,
       rootSubscription: Subscription
     ): Observer<T> {
-      let actionSubscription: Unsubscribable;
+      let actionSubscription: Unsubscribable | undefined;
       let latestValue: T | undefined;
 
       const tryEmitLatestValue = () => {
diff --git a/libs/cdk/tsconfig.lib.json b/libs/cdk/tsconfig.lib.json
index 376bef2c70..4efba27e33 100644
--- a/libs/cdk/tsconfig.lib.json
+++ b/libs/cdk/tsconfig.lib.json
@@ -3,6 +3,10 @@
   "compilerOptions": {
     "target": "es2020",
     "module": "es2015",
+    "strict": true,
+    "forceConsistentCasingInFileNames": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
     "inlineSources": true,
     "importHelpers": true,
     "lib": ["dom", "es2018"]
@@ -14,7 +18,9 @@
     "skipTemplateCodegen": true,
     "strictMetadataEmit": true,
     "fullTemplateTypeCheck": true,
+    "strictTemplates": true,
     "strictInjectionParameters": true,
+    "strictInputAccessModifiers": true,
     "enableResourceInlining": true
   },
   "exclude": [