diff --git a/packages/angular_devkit/core/src/utils/object.ts b/packages/angular_devkit/core/src/utils/object.ts
index 3d5d9edf2475..cf6216032069 100644
--- a/packages/angular_devkit/core/src/utils/object.ts
+++ b/packages/angular_devkit/core/src/utils/object.ts
@@ -6,9 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-export function mapObject<T, V>(obj: {[k: string]: T},
-                                mapper: (k: string, v: T) => V): {[k: string]: V} {
-  return Object.keys(obj).reduce((acc: {[k: string]: V}, k: string) => {
+export function mapObject<T, V>(obj: { [k: string]: T },
+                                mapper: (k: string, v: T) => V): { [k: string]: V } {
+  return Object.keys(obj).reduce((acc: { [k: string]: V }, k: string) => {
     acc[k] = mapper(k, obj[k]);
 
     return acc;
@@ -19,24 +19,33 @@ export function mapObject<T, V>(obj: {[k: string]: T},
 const copySymbol = Symbol();
 
 // tslint:disable-next-line:no-any
-export function deepCopy<T extends any> (value: T): T {
+export function deepCopy<T extends any>(value: T): T {
   if (Array.isArray(value)) {
-    return value.map((o: T) => deepCopy(o));
+    // tslint:disable-next-line:no-any
+    return value.map((o: any) => deepCopy(o)) as unknown as T;
   } else if (value && typeof value === 'object') {
-    if (value[copySymbol]) {
+    const valueCasted = value as {
+      [copySymbol]?: T,
+      toJSON?: () => string,
+      // tslint:disable-next-line:no-any
+      [key: string]: any,
+    };
+
+    if (valueCasted[copySymbol]) {
       // This is a circular dependency. Just return the cloned value.
-      return value[copySymbol];
+      return valueCasted[copySymbol] as T;
     }
-    if (value['toJSON']) {
-      return JSON.parse((value['toJSON'] as () => string)());
+
+    if (valueCasted['toJSON']) {
+      return JSON.parse(valueCasted['toJSON']());
     }
 
-    const copy = new (Object.getPrototypeOf(value).constructor)();
-    value[copySymbol] = copy;
-    for (const key of Object.getOwnPropertyNames(value)) {
-      copy[key] = deepCopy(value[key]);
+    const copy = new (Object.getPrototypeOf(valueCasted).constructor)();
+    valueCasted[copySymbol] = copy;
+    for (const key of Object.getOwnPropertyNames(valueCasted)) {
+      copy[key] = deepCopy(valueCasted[key]);
     }
-    value[copySymbol] = undefined;
+    valueCasted[copySymbol] = undefined;
 
     return copy;
   } else {
diff --git a/packages/ngtools/webpack/src/compiler_host.ts b/packages/ngtools/webpack/src/compiler_host.ts
index 477c40df0a75..eaf9c0421c28 100644
--- a/packages/ngtools/webpack/src/compiler_host.ts
+++ b/packages/ngtools/webpack/src/compiler_host.ts
@@ -361,7 +361,7 @@ export class WebpackCompilerHost implements ts.CompilerHost {
   getCanonicalFileName(fileName: string): string {
     const path = this.resolve(fileName);
 
-    return this.useCaseSensitiveFileNames ? path : path.toLowerCase();
+    return this.useCaseSensitiveFileNames() ? path : path.toLowerCase();
   }
 
   useCaseSensitiveFileNames(): boolean {
diff --git a/packages/ngtools/webpack/src/transformers/replace_resources.ts b/packages/ngtools/webpack/src/transformers/replace_resources.ts
index deb7f0138658..0bfd56a14a4f 100644
--- a/packages/ngtools/webpack/src/transformers/replace_resources.ts
+++ b/packages/ngtools/webpack/src/transformers/replace_resources.ts
@@ -17,7 +17,7 @@ export function replaceResources(
   return (context: ts.TransformationContext) => {
     const typeChecker = getTypeChecker();
 
-    const visitNode: ts.Visitor = (node: ts.Decorator) => {
+    const visitNode: ts.Visitor = (node: ts.Node) => {
       if (ts.isClassDeclaration(node)) {
         const decorators = ts.visitNodes(
           node.decorators,