diff --git a/python/servo/bootstrap_commands.py b/python/servo/bootstrap_commands.py
index 28b5d4fa673..878f01a615e 100644
--- a/python/servo/bootstrap_commands.py
+++ b/python/servo/bootstrap_commands.py
@@ -323,6 +323,8 @@ class MachCommands(CommandBase):
         removing_anything = False
         for tool in ["rust", "cargo"]:
             base = path.join(self.context.sharedir, tool)
+            if not path.isdir(base):
+                continue
             for name in os.listdir(base):
                 # We append `-alt` if LLVM assertions aren't enabled,
                 # so use just the commit hash itself.