diff --git a/packages/compiler-cli/src/ngtsc/shims/src/factory_generator.ts b/packages/compiler-cli/src/ngtsc/shims/src/factory_generator.ts
index 945229f37827a..42377926ed620 100644
--- a/packages/compiler-cli/src/ngtsc/shims/src/factory_generator.ts
+++ b/packages/compiler-cli/src/ngtsc/shims/src/factory_generator.ts
@@ -59,8 +59,12 @@ export class FactoryGenerator implements ShimGenerator {
     let comment: string = '';
     if (original.statements.length > 0) {
       const firstStatement = original.statements[0];
-      if (firstStatement.getLeadingTriviaWidth() > 0) {
-        comment = firstStatement.getFullText().substr(0, firstStatement.getLeadingTriviaWidth());
+      // Must pass SourceFile to getLeadingTriviaWidth(), otherwise it'll try to
+      // get SourceFile by recursively looking up the parent of the Node and fail,
+      // because parent is undefined.
+      const leadingTriviaWidth = firstStatement.getLeadingTriviaWidth(original);
+      if (leadingTriviaWidth > 0) {
+        comment = firstStatement.getFullText().substr(0, leadingTriviaWidth);
       }
     }