diff --git a/ui/build/cleanbuild.go b/ui/build/cleanbuild.go
index 19b5690..65b91bc 100644
--- a/ui/build/cleanbuild.go
+++ b/ui/build/cleanbuild.go
@@ -17,6 +17,7 @@
 import (
 	"bytes"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -46,9 +47,49 @@
 	}
 }
 
+// Based on https://stackoverflow.com/questions/28969455/how-to-properly-instantiate-os-filemode
+// Because Go doesn't provide a nice way to set bits on a filemode
+const (
+	FILEMODE_READ         = 04
+	FILEMODE_WRITE        = 02
+	FILEMODE_EXECUTE      = 01
+	FILEMODE_USER_SHIFT   = 6
+	FILEMODE_USER_READ    = FILEMODE_READ << FILEMODE_USER_SHIFT
+	FILEMODE_USER_WRITE   = FILEMODE_WRITE << FILEMODE_USER_SHIFT
+	FILEMODE_USER_EXECUTE = FILEMODE_EXECUTE << FILEMODE_USER_SHIFT
+)
+
+// Ensures that files and directories in the out dir can be deleted.
+// For example, Bazen can generate output directories where the write bit isn't set, causing 'm' clean' to fail.
+func ensureOutDirRemovable(ctx Context, config Config) {
+	err := filepath.WalkDir(config.OutDir(), func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() {
+			info, err := d.Info()
+			if err != nil {
+				return err
+			}
+			// Equivalent to running chmod u+rwx on each directory
+			newMode := info.Mode() | FILEMODE_USER_READ | FILEMODE_USER_WRITE | FILEMODE_USER_EXECUTE
+			if err := os.Chmod(path, newMode); err != nil {
+				return err
+			}
+		}
+		// Continue walking the out dir...
+		return nil
+	})
+	if err != nil && !os.IsNotExist(err) {
+		// Display the error, but don't crash.
+		ctx.Println(err.Error())
+	}
+}
+
 // Remove everything under the out directory. Don't remove the out directory
 // itself in case it's a symlink.
 func clean(ctx Context, config Config) {
+	ensureOutDirRemovable(ctx, config)
 	removeGlobs(ctx, filepath.Join(config.OutDir(), "*"))
 	ctx.Println("Entire build directory removed.")
 }