diff --git a/src/basic-languages/st/st.contribution.ts b/src/basic-languages/st/st.contribution.ts
index e94b9b67..b6811c7a 100644
--- a/src/basic-languages/st/st.contribution.ts
+++ b/src/basic-languages/st/st.contribution.ts
@@ -10,7 +10,7 @@ declare var require: any;
 
 registerLanguage({
 	id: 'st',
-	extensions: ['.st', '.iecst', '.iecplc', '.lc3lib'],
+	extensions: ['.st', '.iecst', '.iecplc', '.lc3lib', '.TcPOU', '.TcDUT', '.TcGVL', '.TcIO'],
 	aliases: ['StructuredText', 'scl', 'stl'],
 	loader: () => {
 		if (AMD) {
diff --git a/src/basic-languages/st/st.ts b/src/basic-languages/st/st.ts
index fe76f2f1..4ddfdfb7 100644
--- a/src/basic-languages/st/st.ts
+++ b/src/basic-languages/st/st.ts
@@ -172,7 +172,8 @@ export const language = <languages.IMonarchLanguage>{
 		'vendor',
 		'common_source',
 		'from',
-		'extends'
+		'extends',
+		'implements'
 	],
 
 	constant: ['false', 'true', 'null'],