diff --git a/ceph.spec b/ceph.spec
index 8139356..f105d29 100644
--- a/ceph.spec
+++ b/ceph.spec
@@ -1208,10 +1208,11 @@ export CXXFLAGS=$(echo $RPM_OPT_FLAGS | sed -e 's/-Wp,-D_FORTIFY_SOURCE=2//g')
 %endif
 
 # Parallel build settings ...
-CEPH_MFLAGS_JOBS="%{?_smp_mflags}"
 %ifarch s390 s390x
-CEPH_SMP_NCPUS="2"
+CEPH_MFLAGS_JOBS="-j1"
+CEPH_SMP_NCPUS="1"
 %else
+CEPH_MFLAGS_JOBS="%{?_smp_mflags}"
 CEPH_SMP_NCPUS=$(echo "$CEPH_MFLAGS_JOBS" | sed 's/-j//')
 %endif
 %if 0%{?__isa_bits} == 32