diff --git a/src/basic-languages/protobuf/protobuf.ts b/src/basic-languages/protobuf/protobuf.ts
index 50ed4089..a91f13a0 100644
--- a/src/basic-languages/protobuf/protobuf.ts
+++ b/src/basic-languages/protobuf/protobuf.ts
@@ -132,6 +132,10 @@ export const language = <languages.IMonarchLanguage>{
 			[
 				/(")(proto2)(")/,
 				['string.quote', 'string', { token: 'string.quote', switchTo: '@topLevel.proto2' }]
+			],
+			[	 // If no `syntax` provided, regarded as proto2
+			  /.*?/,
+			  { token: '', switchTo: '@topLevel.proto2' }
 			]
 		],