diff --git a/src/basic-languages/csp/csp.contribution.ts b/src/basic-languages/csp/csp.contribution.ts
index 1175ab996e..c5d1379f35 100644
--- a/src/basic-languages/csp/csp.contribution.ts
+++ b/src/basic-languages/csp/csp.contribution.ts
@@ -10,7 +10,7 @@ declare var require: any;
 
 registerLanguage({
 	id: 'csp',
-	extensions: [],
+	extensions: ['.csp'],
 	aliases: ['CSP', 'csp'],
 	loader: () => {
 		if (AMD) {