diff --git a/src/parsers/marker.parser.ts b/src/parsers/marker.parser.ts
index 9ec5d32..19bd52d 100644
--- a/src/parsers/marker.parser.ts
+++ b/src/parsers/marker.parser.ts
@@ -9,7 +9,7 @@ const MARKER_PACKAGE_IMPORT_NAME = 'marker';
 
 export class MarkerParser implements ParserInterface {
 
-	public extract(contents: string, filePath: string): TranslationCollection {
+	public extract(contents: string, filePath: string): TranslationCollection | null {
 		const sourceFile = tsquery.ast(contents, filePath);
 
 		const markerFnName = getNamedImportAlias(sourceFile, MARKER_PACKAGE_MODULE_NAME, MARKER_PACKAGE_IMPORT_NAME);
diff --git a/src/parsers/parser.interface.ts b/src/parsers/parser.interface.ts
index bc395d0..71b2aa0 100644
--- a/src/parsers/parser.interface.ts
+++ b/src/parsers/parser.interface.ts
@@ -2,6 +2,6 @@ import { TranslationCollection } from '../utils/translation.collection';
 
 export interface ParserInterface {
 
-	extract(template: string, path: string): TranslationCollection;
+	extract(source: string, filePath: string): TranslationCollection | null;
 
 }
diff --git a/src/parsers/service.parser.ts b/src/parsers/service.parser.ts
index 9e2f06c..bd8af97 100644
--- a/src/parsers/service.parser.ts
+++ b/src/parsers/service.parser.ts
@@ -9,7 +9,7 @@ const TRANSLATE_SERVICE_METHOD_NAMES = ['get', 'instant', 'stream'];
 
 export class ServiceParser implements ParserInterface {
 
-	public extract(source: string, filePath: string): TranslationCollection {
+	public extract(source: string, filePath: string): TranslationCollection | null {
 		const sourceFile = tsquery.ast(source, filePath);
 
 		const classNodes = findClasses(sourceFile);