diff --git a/arduino-ide-extension/src/browser/create/create-api.ts b/arduino-ide-extension/src/browser/create/create-api.ts
index 55a5d6387..8c2e4281a 100644
--- a/arduino-ide-extension/src/browser/create/create-api.ts
+++ b/arduino-ide-extension/src/browser/create/create-api.ts
@@ -15,6 +15,47 @@ export namespace ResponseResultProvider {
   export const JSON: ResponseResultProvider = (response) => response.json();
 }
 
+export function Utf8ArrayToStr(array: Uint8Array): string {
+  let out, i, c;
+  let char2, char3;
+
+  out = '';
+  const len = array.length;
+  i = 0;
+  while (i < len) {
+    c = array[i++];
+    switch (c >> 4) {
+      case 0:
+      case 1:
+      case 2:
+      case 3:
+      case 4:
+      case 5:
+      case 6:
+      case 7:
+        // 0xxxxxxx
+        out += String.fromCharCode(c);
+        break;
+      case 12:
+      case 13:
+        // 110x xxxx   10xx xxxx
+        char2 = array[i++];
+        out += String.fromCharCode(((c & 0x1f) << 6) | (char2 & 0x3f));
+        break;
+      case 14:
+        // 1110 xxxx  10xx xxxx  10xx xxxx
+        char2 = array[i++];
+        char3 = array[i++];
+        out += String.fromCharCode(
+          ((c & 0x0f) << 12) | ((char2 & 0x3f) << 6) | ((char3 & 0x3f) << 0)
+        );
+        break;
+    }
+  }
+
+  return out;
+}
+
 type ResourceType = 'f' | 'd';
 
 @injectable()
@@ -275,9 +316,7 @@ export class CreateApi {
 
         // parse the secret file
         const secrets = (
-          typeof content === 'string'
-            ? content
-            : new TextDecoder().decode(content)
+          typeof content === 'string' ? content : Utf8ArrayToStr(content)
         )
           .split(/\r?\n/)
           .reduce((prev, curr) => {
@@ -341,7 +380,7 @@ export class CreateApi {
     const headers = await this.headers();
 
     let data: string =
-      typeof content === 'string' ? content : new TextDecoder().decode(content);
+      typeof content === 'string' ? content : Utf8ArrayToStr(content);
     data = await this.toggleSecretsInclude(posixPath, data, 'remove');
 
     const payload = { data: btoa(data) };