diff --git a/firefox.spec b/firefox.spec
index 34a377b..1032c30 100644
--- a/firefox.spec
+++ b/firefox.spec
@@ -55,7 +55,7 @@ Patch43:        firefox-2.0-getstartpage.patch
 
 # ---------------------------------------------------
 
-BuildRoot:      %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)
+BuildRoot:      %(mktemp -ud %{_tmppath}/%{name}-%{version}-%{release}-XXXXXX)
 BuildRequires:  libIDL-devel
 BuildRequires:  desktop-file-utils
 BuildRequires:  gtk2-devel