diff --git a/macros b/macros
index cf4819d..05e3169 100644
--- a/macros
+++ b/macros
@@ -131,6 +131,12 @@ print(result)
 %__global_fcflags %{build_fflags}
 %__global_ldflags %{build_ldflags}
 
+# Architecture-specific support.  Internal.  Do not use directly.
+
+# Also used for s390.
+__cflags_arch_s390x \
+%[0%{?rhel} >= 8 ? "-march=z13 -mtune=z13" : "-march=zEC12 -mtune=z13"]
+
 #==============================================================================
 # ---- configure and makeinstall.
 #
diff --git a/rpmrc b/rpmrc
index c0bad81..a831b9e 100644
--- a/rpmrc
+++ b/rpmrc
@@ -71,8 +71,8 @@ optflags: atariclone %{__global_compiler_flags}
 optflags: milan %{__global_compiler_flags}
 optflags: hades %{__global_compiler_flags}
 
-optflags: s390 %{__global_compiler_flags} -m31 -march=zEC12 -mtune=z13 -fasynchronous-unwind-tables
-optflags: s390x %{__global_compiler_flags} -m64 -march=zEC12 -mtune=z13 -fasynchronous-unwind-tables -fstack-clash-protection
+optflags: s390 %{__global_compiler_flags} -m31 %{__cflags_arch_s390x} -fasynchronous-unwind-tables
+optflags: s390x %{__global_compiler_flags} -m64 %{__cflags_arch_s390x} -fasynchronous-unwind-tables -fstack-clash-protection
 
 optflags: aarch64 %{__global_compiler_flags} -mbranch-protection=standard -fasynchronous-unwind-tables %[ "%{toolchain}" == "gcc" ? "-fstack-clash-protection" : "" ]