diff --git a/Rakefile b/Rakefile
index 0c3b2c0..cb79c19 100755
--- a/Rakefile
+++ b/Rakefile
@@ -85,6 +85,13 @@ end
 directory DOWNLOAD_DIR
 directory PROB_DIR
 
+desc "Build zip file"
+task :zip => [:clobber_zip, ZIP_FILE]
+
+task :clobber_zip do
+  rm ZIP_FILE
+end
+
 file ZIP_FILE => KOAN_FILES + [DOWNLOAD_DIR] do
   sh "zip #{ZIP_FILE} #{PROB_DIR}/*"
 end