diff --git a/zlib.spec b/zlib.spec
index 03f5469..436e811 100644
--- a/zlib.spec
+++ b/zlib.spec
@@ -2,7 +2,7 @@
 
 Name:    zlib
 Version: 1.2.11
-Release: 28%{?dist}
+Release: 29%{?dist}
 Summary: Compression and decompression library
 # /contrib/dotzlib/ have Boost license
 License: zlib and Boost
@@ -110,6 +110,7 @@ mv ChangeLog.tmp ChangeLog
 
 
 %build
+export CFLAGS="$RPM_OPT_FLAGS"
 
 export LDFLAGS="$LDFLAGS -Wl,-z,relro -Wl,-z,now"
 # no-autotools, %%configure is not compatible
@@ -179,6 +180,9 @@ find $RPM_BUILD_ROOT -name '*.la' -delete
 
 
 %changelog
+* Thu Jul 15 2021 Ondrej Dubaj <odubaj@redhat.com> - 1.2.11-29
+- Missing RPM_OPT_FLAGS in CFLAGS (#1972057)
+
 * Thu Jun 03 2021 Patrik Novotný <panovotn@redhat.com> - 1.2.11-28
 - IBM CRC32 optimalization rhbz#1959423
 - Enabled Z hardware-accelerated deflate for compression levels 1 through 6 (#1972057)