diff --git a/thunderbird.spec b/thunderbird.spec
index 18025ef..e4c8506 100644
--- a/thunderbird.spec
+++ b/thunderbird.spec
@@ -278,7 +278,7 @@ export LIBDIR='%{_libdir}'
 MOZ_SMP_FLAGS=-j1
 # On x86 architectures, Mozilla can build up to 4 jobs at once in parallel,
 # however builds tend to fail on other arches when building in parallel.
-%ifarch %{ix86} x86_64
+%ifarch %{ix86} x86_64 ppc ppc64
 [ -z "$RPM_BUILD_NCPUS" ] && \
      RPM_BUILD_NCPUS="`/usr/bin/getconf _NPROCESSORS_ONLN`"
 [ "$RPM_BUILD_NCPUS" -ge 2 ] && MOZ_SMP_FLAGS=-j2