diff --git a/bob/devtools/bootstrap.py b/bob/devtools/bootstrap.py
index 456d884ca109a6dd3912ccf487e7c7b52c2594b7..59b2e2aa8d2caf35c6ead9a5a08a70b9fa6d425f 100644
--- a/bob/devtools/bootstrap.py
+++ b/bob/devtools/bootstrap.py
@@ -509,6 +509,9 @@ if __name__ == "__main__":
 
     if args.command == "build":
 
+        # clean conda cache and packages before building
+        run_cmdline([conda_bin, "clean", "--all"])
+
         # simple - just use the defaults channels when self building
         run_cmdline(
             [conda_bin, "install", "--yes"]