diff --git a/src/providers/hover/_base.ts b/src/providers/hover/_base.ts
index 791bf24..6b3bf07 100644
--- a/src/providers/hover/_base.ts
+++ b/src/providers/hover/_base.ts
@@ -12,7 +12,7 @@ export abstract class HoverProvider implements vscode.HoverProvider, vscode.Disp
 
     constructor(
         /** A selector that defines the documents this provider is applicable to */
-        private documentSelector: vscode.DocumentSelector
+        private readonly documentSelector: vscode.DocumentSelector
     ) { }
 
     /**
diff --git a/src/providers/hover/localization.ts b/src/providers/hover/localization.ts
index 5fee0c7..85a1d00 100644
--- a/src/providers/hover/localization.ts
+++ b/src/providers/hover/localization.ts
@@ -18,7 +18,7 @@ export class LocalizationHoverProvider extends HoverProvider {
     private static references: Map<string, string> = new Map();
 
     /** A selector that defines the documents this provider is applicable to */
-    private static documentSelector: vscode.DocumentSelector = ['xml'];
+    private static readonly documentSelector: vscode.DocumentSelector = ['xml'];
 
     constructor() {
         super(LocalizationHoverProvider.documentSelector);
diff --git a/src/providers/hover/version.ts b/src/providers/hover/version.ts
index c63331f..1cc66df 100644
--- a/src/providers/hover/version.ts
+++ b/src/providers/hover/version.ts
@@ -14,7 +14,7 @@ import { HoverProvider } from './_base';
 export class VersionHoverProvider extends HoverProvider {
 
     /** A selector that defines the documents this provider is applicable to */
-    private static documentSelector = ['xml'];
+    private static readonly documentSelector = ['xml'];
 
     constructor() {
         super(VersionHoverProvider.documentSelector);