diff --git a/addons/xterm-addon-webgl/src/WebglRenderer.api.ts b/addons/xterm-addon-webgl/src/WebglRenderer.api.ts
index 7165edb3..64ad06a1 100644
--- a/addons/xterm-addon-webgl/src/WebglRenderer.api.ts
+++ b/addons/xterm-addon-webgl/src/WebglRenderer.api.ts
@@ -16,14 +16,12 @@ let page: Page;
 const width = 800;
 const height = 600;
 
-let itWebgl: (expectation: string, callback?: (this: Mocha.ITestCallbackContext, done: MochaDone) => any) => Mocha.ITest | void;
-
 describe('WebGL Renderer Integration Tests', async () => {
   const browserType = getBrowserType();
   const isHeadless = process.argv.indexOf('--headless') !== -1;
   // Firefox works only in non-headless mode https://github.com/microsoft/playwright/issues/1032
   const areTestsEnabled = browserType.name() === 'chromium' || (browserType.name() === 'firefox' && !isHeadless);
-  itWebgl = areTestsEnabled ? it : it.skip;
+  const itWebgl = areTestsEnabled ? it : it.skip;
 
   itWebgl('dispose removes renderer canvases', async function(): Promise<void> {
     await setupBrowser();
diff --git a/package.json b/package.json
index 6f978b68..bd01b57d 100644
--- a/package.json
+++ b/package.json
@@ -41,7 +41,7 @@
     "@types/deep-equal": "^1.0.1",
     "@types/glob": "^7.1.3",
     "@types/jsdom": "^16.2.3",
-    "@types/mocha": "^7.0.2",
+    "@types/mocha": "^8.0.0",
     "@types/node": "^10.17.17",
     "@types/utf8": "^2.1.6",
     "@types/webpack": "^4.41.21",
diff --git a/src/browser/Linkifier.test.ts b/src/browser/Linkifier.test.ts
index 81741df4..2567a669 100644
--- a/src/browser/Linkifier.test.ts
+++ b/src/browser/Linkifier.test.ts
@@ -59,7 +59,7 @@ describe('Linkifier', () => {
     bufferService.buffer.lines.push(stringToRow(text));
   }
 
-  function assertLinkifiesRow(rowText: string, linkMatcherRegex: RegExp, links: {x: number, length: number}[], done: MochaDone): void {
+  function assertLinkifiesRow(rowText: string, linkMatcherRegex: RegExp, links: {x: number, length: number}[], done: Mocha.Done): void {
     addRow(rowText);
     linkifier.registerLinkMatcher(linkMatcherRegex, () => {});
     linkifier.linkifyRows();
@@ -76,7 +76,7 @@ describe('Linkifier', () => {
     }, 0);
   }
 
-  function assertLinkifiesMultiLineLink(rowText: string, linkMatcherRegex: RegExp, links: {x1: number, y1: number, x2: number, y2: number}[], done: MochaDone): void {
+  function assertLinkifiesMultiLineLink(rowText: string, linkMatcherRegex: RegExp, links: {x1: number, y1: number, x2: number, y2: number}[], done: Mocha.Done): void {
     addRow(rowText);
     linkifier.registerLinkMatcher(linkMatcherRegex, () => {});
     linkifier.linkifyRows();
diff --git a/src/browser/Terminal.test.ts b/src/browser/Terminal.test.ts
index f192b031..9bdc783e 100644
--- a/src/browser/Terminal.test.ts
+++ b/src/browser/Terminal.test.ts
@@ -1042,7 +1042,7 @@ describe('Terminal', () => {
       linkifier.attachToDom({} as any, mouseZoneManager);
     });
 
-    function assertLinkifiesInTerminal(rowText: string, linkMatcherRegex: RegExp, links: {x1: number, y1: number, x2: number, y2: number}[], done: MochaDone): void {
+    function assertLinkifiesInTerminal(rowText: string, linkMatcherRegex: RegExp, links: {x1: number, y1: number, x2: number, y2: number}[], done: Mocha.Done): void {
       terminal.writeSync(rowText);
       linkifier.registerLinkMatcher(linkMatcherRegex, () => {});
       linkifier.linkifyRows();
diff --git a/yarn.lock b/yarn.lock
index 1473a44b..24b4f71f 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -278,10 +278,10 @@
   resolved "https://registry.yarnpkg.com/@types/mocha/-/mocha-5.2.7.tgz#315d570ccb56c53452ff8638738df60726d5b6ea"
   integrity sha512-NYrtPht0wGzhwe9+/idPaBB+TqkY9AhTvOLMkThm0IoEfLaiVQZwBwyJ5puCkO3AUCWrmcoePjp2mbFocKy4SQ==
 
-"@types/mocha@^7.0.2":
-  version "7.0.2"
-  resolved "https://registry.yarnpkg.com/@types/mocha/-/mocha-7.0.2.tgz#b17f16cf933597e10d6d78eae3251e692ce8b0ce"
-  integrity sha512-ZvO2tAcjmMi8V/5Z3JsyofMe3hasRcaw88cto5etSVMwVQfeivGAlEYmaQgceUSVYFofVjT+ioHsATjdWcFt1w==
+"@types/mocha@^8.0.0":
+  version "8.0.0"
+  resolved "https://registry.yarnpkg.com/@types/mocha/-/mocha-8.0.0.tgz#b0ba1c5b4cb3880c51a6b488ad007a657d1be888"
+  integrity sha512-jWeYcTo3sCH/rMgsdYXDTO85GNRyTCII5dayMIu/ZO4zbEot1E3iNGaOwpLReLUHjeNQFkgeNNVYlY4dX6azQQ==
 
 "@types/node@*":
   version "13.9.5"