diff --git a/MozillaThunderbird.spec b/MozillaThunderbird.spec
index 858cce9..2b0977a 100644
--- a/MozillaThunderbird.spec
+++ b/MozillaThunderbird.spec
@@ -223,9 +223,6 @@ export CFLAGS="$RPM_OPT_FLAGS -fno-strict-aliasing"
 %if 0%{?suse_version} > 1320
 export CFLAGS="$CFLAGS -fno-delete-null-pointer-checks"
 %endif
-%if %{with mozilla_tb_optimize_for_size}
-export CFLAGS="$CFLAGS -Os"
-%endif
 %ifarch ppc64 ppc64le
 export CFLAGS="$CFLAGS -mminimal-toc"
 %endif