diff --git a/tools/idf_monitor.py b/tools/idf_monitor.py
index 38bfce980..f9eb2d1bd 100755
--- a/tools/idf_monitor.py
+++ b/tools/idf_monitor.py
@@ -733,8 +733,10 @@ if os.name == 'nt':
                 pass
 
         def write(self, data):
-            if type(data) is not bytes:
-                data = data.encode('latin-1')
+            if isinstance(data, bytes):
+                data = bytearray(data)
+            else:
+                data = bytearray(data, 'utf-8')
             for b in data:
                 b = bytes([b])
                 l = len(self.matched)