diff --git a/virtualbox.spec b/virtualbox.spec
index 419ca07..e107356 100644
--- a/virtualbox.spec
+++ b/virtualbox.spec
@@ -593,7 +593,7 @@ install -m 644 UnattendedTemplates/*		%{buildroot}%{_datadir}/virtualbox/Unatten
 # install kmp src
 mkdir -p %{buildroot}%{_usrsrc}/kernel-modules/virtualbox
 mkdir -p %{buildroot}%{_usrsrc}/kernel-modules/additions
-tar jcf %{buildroot}%{_usrsrc}/kernel-modules/additions/guest_src.tar.bz2 additions/src
+tar -jcf %{buildroot}%{_usrsrc}/kernel-modules/additions/guest_src.tar.bz2 additions/src
 cp -a src %{buildroot}%{_usrsrc}/kernel-modules/virtualbox
 install -m 644 %{SOURCE11}			%{buildroot}%{_udevrulesdir}/60-vboxdrv.rules
 popd