diff --git a/thunderbird.spec b/thunderbird.spec
index 60eb196..e8890f9 100644
--- a/thunderbird.spec
+++ b/thunderbird.spec
@@ -273,7 +273,7 @@ MOZ_OPT_FLAGS="$MOZ_OPT_FLAGS -Wformat-security -Wformat -Werror=format-security
 MOZ_OPT_FLAGS=$(echo "$MOZ_OPT_FLAGS" | %{__sed} -e 's/-O2//')
 %endif
 %ifarch s390
-MOZ_OPT_FLAGS=$(echo "$RPM_OPT_FLAGS" | %{__sed} -e 's/-g/-g1/')
+MOZ_OPT_FLAGS=$(echo "$MOZ_OPT_FLAGS" | %{__sed} -e 's/-g/-g1/')
 %endif
 %ifarch s390 %{arm} ppc aarch64
 MOZ_LINK_FLAGS="-Wl,--no-keep-memory -Wl,--reduce-memory-overheads"