diff --git a/xxhash.spec b/xxhash.spec
index a1bf827..7d88ab3 100644
--- a/xxhash.spec
+++ b/xxhash.spec
@@ -59,30 +59,32 @@ Headers and other development files for xxHash.
 %autosetup -p1 -n xxHash-%{version}
 
 %build
+# upstream make -O3 mandatory to get performance gain
+tmpflags="$(echo %{optflags} | sed 's,-O2,-O3,g')"
 # ALLOW_AVX just means "we guarantee we policed our %%optflags".
-export CFLAGS="%{optflags} -DXXH_X86DISPATCH_ALLOW_AVX=1"
-export CXXFLAGS="$CFLAGS"
+export CFLAGS="${tmpflags} -DXXH_X86DISPATCH_ALLOW_AVX=1"
+export CXXFLAGS="${CFLAGS}"
 export LDFLAGS="%{?build_ldflags}"
 # DISPATCH=1 if you want AVX2/AVX512. But it does not seem to perform any
 # better than the lowest-denomimation code on at least the 1135G7 and 5950X
 # CPUs, and for both LP64 as well as ILP32 — it seems to be all within margin
 # of error.
-%make_build prefix=%{_prefix} libdir=%{_libdir}
+%make_build prefix=%{_prefix} libdir=%{_libdir} DISPATCH=1
 
 %install
-export CFLAGS="%{optflags} -DXXH_X86DISPATCH_ALLOW_AVX=1"
-export CXXFLAGS="%{optflags}"
+export CFLAGS="${tmpflags} -DXXH_X86DISPATCH_ALLOW_AVX=1"
+export CXXFLAGS="${CFLAGS}"
 export LDFLAGS="%{?build_ldflags}"
-%make_install prefix=%{_prefix} libdir=%{_libdir}
+%make_install prefix=%{_prefix} libdir=%{_libdir} DISPATCH=1
 rm -rf %{buildroot}%{_libdir}/libxxhash.a
 
 %check
-export CFLAGS="%{optflags}"
-export CXXFLAGS="%{optflags}"
+export CFLAGS="${tmpflags}"
+export CXXFLAGS="${CFLAGS}"
 export LDFLAGS="%{?build_ldflags}"
 # not safe for parallel execution as it removes xxhash.o and recreates it with different flags
 # the list is taken from test-all with non-working/irrelevant ones (such as ones that change the toolchain) removed
-%make_build -j1 test test-unicode listL120 trailingWhitespace test-xxh-nnn-sums
+%make_build -j1 DISPATCH=1 test test-unicode listL120 trailingWhitespace test-xxh-nnn-sums
 
 %ldconfig_scriptlets -n libxxhash0
 
@@ -104,6 +106,7 @@ export LDFLAGS="%{?build_ldflags}"
 %files devel
 %{_includedir}/xxhash.h
 %{_includedir}/xxh3.h
+%{_includedir}/xxh_x86dispatch.h
 %{_libdir}/pkgconfig/libxxhash.pc
 %{_libdir}/libxxhash.so