diff --git a/lib/health-check.js b/lib/health-check.js
index 08fc811..4f696bf 100644
--- a/lib/health-check.js
+++ b/lib/health-check.js
@@ -19,7 +19,7 @@ const livenessURL = process.env.LIVENESS_URL || LIVENESS_URL;
 const protect = protection('http', protectCfg);
 
 function callProtect(request, reply) {
-  reply.header('Content-Type', 'text/plain; charset=utf8');
+  reply.header('Content-Type', 'text/plain; charset=utf-8');
   protect(request, reply, _ => reply.send('OK'));
 }
 
diff --git a/lib/invoker.js b/lib/invoker.js
index 361a5ad..e8ab08c 100644
--- a/lib/invoker.js
+++ b/lib/invoker.js
@@ -10,7 +10,7 @@ module.exports = function invoker(func) {
       code: 200,
       response: undefined,
       headers: {
-        'content-type': 'application/json; charset=utf8',
+        'content-type': 'application/json; charset=utf-8',
         'access-control-allow-methods':
           'OPTIONS, GET, DELETE, POST, PUT, HEAD, PATCH',
         'access-control-allow-origin': '*'
@@ -71,7 +71,7 @@ module.exports = function invoker(func) {
     // If the function returns a string, set the content type to text/plain
     // and return it as the response
     if (typeof fnReturn === 'string') {
-      payload.headers['content-type'] = 'text/plain; charset=utf8';
+      payload.headers['content-type'] = 'text/plain; charset=utf-8';
       payload.response = fnReturn;
       return payload;
     }
@@ -97,15 +97,15 @@ module.exports = function invoker(func) {
       // Provide default content-type unless supplied by user
       if (!payload.headers || !payload.headers['content-type']) {
         if (typeof fnReturn.body === 'string') {
-          payload.headers['content-type'] = 'text/plain; charset=utf8';
+          payload.headers['content-type'] = 'text/plain; charset=utf-8';
         } else if (typeof fnReturn.body === 'object') {
-          payload.headers['content-type'] = 'application/json; charset=utf8';
+          payload.headers['content-type'] = 'application/json; charset=utf-8';
         }
       }
       payload.response = fnReturn.body;
     } else if (typeof fnReturn === 'object' && !fnReturn?.body) {
       // Finally, the user may have supplied a simple object response
-      payload.headers['content-type'] = 'application/json; charset=utf8';
+      payload.headers['content-type'] = 'application/json; charset=utf-8';
       payload.response = fnReturn;
     }
     return payload;