diff --git a/src/pylorax/imgutils.py b/src/pylorax/imgutils.py
index 32e99b9d..4cf0370c 100644
--- a/src/pylorax/imgutils.py
+++ b/src/pylorax/imgutils.py
@@ -150,7 +150,7 @@ def loop_attach(outfile):
     dev = runcmd_output(["losetup", "--find", "--show", outfile])
 
     # Sometimes the loop device isn't ready yet, make extra sure before returning
-    loop_waitfor(dev, outfile)
+    loop_waitfor(dev.strip(), outfile)
     return dev.strip()
 
 def loop_detach(loopdev):