kmx.io/rbpkg

diff --git a/lib/rbpkg/repo.rb b/lib/rbpkg/repo.rb
index 0c61ead..120c341 100644
--- a/lib/rbpkg/repo.rb
+++ b/lib/rbpkg/repo.rb
@@ -57,7 +57,7 @@ class Rbpkg::Repo
     sh_ci_profile = sh_quote(ci_dir + '/etc/profile')
     cmd! "#{sh_quote(Rbpkg.dir)}/bin/rbpkg_bootstrap -f #{sh_quote(ci_dir)}"
     cmd! "export RBPKG_DIR=#{sh_ci_dir} && . #{sh_ci_profile} && rbpkg clone #{sh_name}"
-    cmd! "export RBPKG_DIR=#{sh_ci_dir} && . #{sh_ci_profile} && rbpkg checkout #{sh_quote(commit)} #{sh_name}"
+    cmd! "export RBPKG_DIR=#{sh_ci_dir} && . #{sh_ci_profile} && rbpkg checkout #{sh_quote(commit)} #{sh_name}" if commit
     cmd! "export RBPKG_DIR=#{sh_ci_dir} && . #{sh_ci_profile} && rbpkg info #{sh_name}"
     cmd! "export RBPKG_DIR=#{sh_ci_dir} && . #{sh_ci_profile} && rbpkg configure #{sh_name}"
     cmd! "export RBPKG_DIR=#{sh_ci_dir} && . #{sh_ci_profile} && rbpkg build #{sh_name}"