diff --git a/fsl/utils/callfsl.py b/fsl/utils/callfsl.py
index fa68a3f4d4fdb46324de5484563de8976114c7f5..d86856ebebef11420d85623d357d875b8dc96fd7 100644
--- a/fsl/utils/callfsl.py
+++ b/fsl/utils/callfsl.py
@@ -42,7 +42,7 @@ def callFSL(*args):
 
     log.debug('callfsl: {}'.format(' '.join(args)))
 
-    result = sp.check_output(args)
+    result = sp.check_output(args).decode('utf-8')
 
     log.debug('result: {}'.format(result))