diff --git a/rubygem-open4.spec b/rubygem-open4.spec
index 63da4fa..713f281 100644
--- a/rubygem-open4.spec
+++ b/rubygem-open4.spec
@@ -34,7 +34,7 @@ Documentation for %{name}
 %install
 rm -rf %{buildroot}
 mkdir -p %{buildroot}%{gem_dir}
-%gem_install -n %{SOURCE0}
+%gem_install -n %{SOURCE0} -d %{buildroot}%{gem_dir}
 
 %check
 pushd %{buildroot}%{gem_instdir}