diff --git a/ext_scripts/ext_rbd.py b/ext_scripts/ext_rbd.py
index a54f96dae14578aafd5bd11394391e92e3cb6add..199c27dcb6606e170405d45b9a302c72a4866562 100755
--- a/ext_scripts/ext_rbd.py
+++ b/ext_scripts/ext_rbd.py
@@ -66,7 +66,7 @@ PREFIX_USP = 'usp_'
 def cmd_open(cmd, bufsize=-1, env=None):
     inst = subprocess.Popen(cmd, shell=False, bufsize=bufsize,
                             stdin=subprocess.PIPE, stdout=subprocess.PIPE,
-                            stderr=subprocess.PIPE, close_fds=True)
+                            stderr=subprocess.PIPE, close_fds=True, text=True)
     return inst