diff --git a/xz.spec b/xz.spec
index a526fd4..4fd9e50 100644
--- a/xz.spec
+++ b/xz.spec
@@ -83,12 +83,9 @@ commands that deal with the older LZMA format.
 
 
 %build
-CFLAGS="%{optflags} -D_FILE_OFFSET_BITS=64"
 %ifarch %{power64}
-    CFLAGS=`echo $CFLAGS | xargs -n 1 | sed 's|^-O2$|-O3|g' | xargs -n 100`
+export CFLAGS="%{optflags} -O3"
 %endif
-export CFLAGS
-
 %configure
 sed -i 's|^hardcode_libdir_flag_spec=.*|hardcode_libdir_flag_spec=""|g' libtool
 sed -i 's|^runpath_var=LD_RUN_PATH|runpath_var=DIE_RPATH_DIE|g' libtool
@@ -152,6 +149,7 @@ LD_LIBRARY_PATH=$PWD/src/liblzma/.libs make check
 - drop ppc64p7 hack, per fedora devel list discussion:
   https://lists.fedoraproject.org/archives/list/
   devel@lists.fedoraproject.org/thread/2OWD2QRDFBEC6HTPVQ7FMJENH32BWT54/
+- don't explicitly set _FILE_OFFSET_BITS, package uses AC_SYS_LARGEFILE
 
 * Tue May 08 2018 Pavel Raiskup <praiskup@redhat.com> - 5.2.4-1
 - rebase to 5.2.4 (rhbz#1574039), per release notes: