Index: nss/lib/freebl/verified/kremlin/include/kremlin/internal/types.h
===================================================================
--- nss.orig/lib/freebl/verified/kremlin/include/kremlin/internal/types.h
+++ nss/lib/freebl/verified/kremlin/include/kremlin/internal/types.h
@@ -56,9 +56,10 @@ typedef const char *Prims_string;
     !defined(__clang__)
 #include <emmintrin.h>
 typedef __m128i FStar_UInt128_uint128;
-#elif !defined(KRML_VERIFIED_UINT128) && !defined(_MSC_VER) &&           \
+#elif !defined(KRML_VERIFIED_UINT128) && !defined(_MSC_VER) && \
     (defined(__x86_64__) || defined(__x86_64) || defined(__aarch64__) || \
-     (defined(__powerpc64__) && defined(__LITTLE_ENDIAN__)))
+    (defined(__powerpc64__) && defined(__LITTLE_ENDIAN__)) || \
+     defined(__s390x__))
 typedef unsigned __int128 FStar_UInt128_uint128;
 #elif !defined(KRML_VERIFIED_UINT128) && defined(_MSC_VER) && defined(__clang__)
 typedef __uint128_t FStar_UInt128_uint128;
Index: nss/lib/freebl/verified/kremlin/kremlib/dist/minimal/fstar_uint128_gcc64.h
===================================================================
--- nss.orig/lib/freebl/verified/kremlin/kremlib/dist/minimal/fstar_uint128_gcc64.h
+++ nss/lib/freebl/verified/kremlin/kremlib/dist/minimal/fstar_uint128_gcc64.h
@@ -26,7 +26,8 @@
 
 #if !defined(KRML_VERIFIED_UINT128) && (!defined(_MSC_VER) || defined(__clang__)) && \
     (defined(__x86_64__) || defined(__x86_64) || defined(__aarch64__) ||             \
-     (defined(__powerpc64__) && defined(__LITTLE_ENDIAN__)))
+    (defined(__powerpc64__) && defined(__LITTLE_ENDIAN__)) || \
+     defined(__s390x__))
 
 /* GCC + using native unsigned __int128 support */