diff --git a/openvdb.spec b/openvdb.spec
index 3a01a7b..42e3d57 100644
--- a/openvdb.spec
+++ b/openvdb.spec
@@ -20,6 +20,9 @@ URL:            http://www.openvdb.org/
 
 Source0:        https://github.com/AcademySoftwareFoundation/%{name}/archive/v%{version}/%{name}-%{version}.tar.gz
 
+# OpenVDB no longer builds on 32bits with latest TBB due to OOM.
+ExcludeArch:    i686
+
 BuildRequires:  boost-devel >= 1.61
 # boost-python3-devel merged in boost-devel for Fedora 33+
 # https://src.fedoraproject.org/rpms/boost/c/1f2e448e099a867f9da62b9da009d3dec5e1ad64?branch=master
@@ -147,9 +150,10 @@ export CXXFLAGS="%{build_cxxflags} -Wl,--as-needed"
     -DUSE_EXR=ON \
 %endif
     -DUSE_NANOVDB=ON
-# Increase memory usage to 8GB for a successful
-# build on ppc64le architecture
-%cmake_build %limit_build -m 10240
+
+# Increase memory reserve to 12GB per build thread for a successful build on
+# ppc64le and s390x.
+%cmake_build %limit_build -m 12288
 
 %if 0%{?with_tests}
 %check