diff --git a/guacamole-common-js/src/main/resources/tunnel.js b/guacamole-common-js/src/main/resources/tunnel.js
index 5cec1be01..b66d830f5 100644
--- a/guacamole-common-js/src/main/resources/tunnel.js
+++ b/guacamole-common-js/src/main/resources/tunnel.js
@@ -182,7 +182,7 @@ Guacamole.HTTPTunnel = function(tunnelURL) {
 
             var message_xmlhttprequest = new XMLHttpRequest();
             message_xmlhttprequest.open("POST", TUNNEL_WRITE + tunnel_uuid);
-            message_xmlhttprequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
+            message_xmlhttprequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded; charset=UTF-8");
 
             // Once response received, send next queued event.
             message_xmlhttprequest.onreadystatechange = function() {
@@ -456,7 +456,7 @@ Guacamole.HTTPTunnel = function(tunnelURL) {
         // Start tunnel and connect synchronously
         var connect_xmlhttprequest = new XMLHttpRequest();
         connect_xmlhttprequest.open("POST", TUNNEL_CONNECT, false);
-        connect_xmlhttprequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
+        connect_xmlhttprequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded; charset=UTF-8");
         connect_xmlhttprequest.send(data);
 
         // If failure, throw error
diff --git a/guacamole/src/main/webapp/scripts/service.js b/guacamole/src/main/webapp/scripts/service.js
index df99f6cf0..af330c6e5 100644
--- a/guacamole/src/main/webapp/scripts/service.js
+++ b/guacamole/src/main/webapp/scripts/service.js
@@ -348,7 +348,7 @@ GuacamoleService.Connections = {
         // Add user
         var xhr = new XMLHttpRequest();
         xhr.open("POST", users_url, false);
-        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
+        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded; charset=UTF-8");
         xhr.send(data);
 
         // Handle response
@@ -381,7 +381,7 @@ GuacamoleService.Connections = {
         // Add user
         var xhr = new XMLHttpRequest();
         xhr.open("POST", users_url, false);
-        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
+        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded; charset=UTF-8");
         xhr.send(data);
 
         // Handle response
@@ -535,7 +535,7 @@ GuacamoleService.Users = {
         // Update user
         var xhr = new XMLHttpRequest();
         xhr.open("POST", users_url, false);
-        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
+        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded; charset=UTF-8");
         xhr.send(data);
 
         // Handle response
@@ -628,7 +628,7 @@ GuacamoleService.Permissions = {
         // Get permission list
         var xhr = new XMLHttpRequest();
         xhr.open("POST", list_url, false);
-        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
+        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded; charset=UTF-8");
         xhr.send(data);
 
         // Handle response