diff --git a/glib2.spec b/glib2.spec
index ea1ec8e..52e83e0 100644
--- a/glib2.spec
+++ b/glib2.spec
@@ -308,7 +308,8 @@ glib-compile-schemas %{_datadir}/glib-2.0/schemas &> /dev/null || :
 glib-compile-schemas %{_datadir}/glib-2.0/schemas &> /dev/null || :
 
 %check
-make %{?_smp_mflags} check
+# One job at a time. The tests are not safe to run in parallel until 2.60. See: glib!505
+make check
 
 %files -f glib20.lang
 %license COPYING