diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 09239d2288..597bdf0c2d 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8842,6 +8842,7 @@ static int do_getdents64(abi_long dirfd, abi_long arg2, abi_long count)
 #define     RISCV_HWPROBE_EXT_ZVFH          (1 << 30)
 #define     RISCV_HWPROBE_EXT_ZVFHMIN       (1 << 31)
 #define     RISCV_HWPROBE_EXT_ZFA           (1ULL << 32)
+#define     RISCV_HWPROBE_EXT_ZTSO          (1ULL << 33)
 #define     RISCV_HWPROBE_EXT_ZACAS         (1ULL << 34)
 #define     RISCV_HWPROBE_EXT_ZICOND        (1ULL << 35)
 
@@ -8956,6 +8957,8 @@ static void risc_hwprobe_fill_pairs(CPURISCVState *env,
                      RISCV_HWPROBE_EXT_ZVFHMIN : 0;
             value |= cfg->ext_zfa ?
                      RISCV_HWPROBE_EXT_ZFA : 0;
+            value |= cfg->ext_ztso ?
+                     RISCV_HWPROBE_EXT_ZTSO : 0;
             value |= cfg->ext_zacas ?
                      RISCV_HWPROBE_EXT_ZACAS : 0;
             value |= cfg->ext_zicond ?