diff --git a/tools/cdata.js b/tools/cdata.js
index aa473deb..002b9e5d 100644
--- a/tools/cdata.js
+++ b/tools/cdata.js
@@ -132,7 +132,7 @@ function filter(str, type) {
 function specToChunk(srcDir, s) {
   if (s.method == "plaintext") {
     const buf = fs.readFileSync(srcDir + "/" + s.file);
-    const str = buf.toString("ascii");
+    const str = buf.toString("utf-8");
     const chunk = `
 // Autogenerated from ${srcDir}/${s.file}, do not edit!!
 const char ${s.name}[] PROGMEM = R"${s.prepend || ""}${filter(str, s.filter)}${