diff --git a/platformio/commands/home/rpc/handlers/piocore.py b/platformio/commands/home/rpc/handlers/piocore.py
index 44cb6983..940b1dd2 100644
--- a/platformio/commands/home/rpc/handlers/piocore.py
+++ b/platformio/commands/home/rpc/handlers/piocore.py
@@ -51,8 +51,10 @@ class MultiThreadingStdStream(object):
     def write(self, value):
         thread_id = thread_get_ident()
         self._ensure_thread_buffer(thread_id)
+        if PY2 and isinstance(value, unicode):
+            value = value.encode()
         return self._buffers[thread_id].write(
-            value.decode() if not PY2 and is_bytes(value) else value
+            value.decode() if is_bytes(value) else value
         )
 
     def get_value_and_reset(self):