diff --git a/tools/buildman/control.py b/tools/buildman/control.py
index ee96375..8146e1c 100644
--- a/tools/buildman/control.py
+++ b/tools/buildman/control.py
@@ -209,7 +209,7 @@
 
     # Create a new builder with the selected options
     if options.branch:
-        dirname = options.branch
+        dirname = options.branch.replace('/', '_')
     else:
         dirname = 'current'
     output_dir = os.path.join(options.output_dir, dirname)