diff --git a/target/loongarch/tcg/csr_helper.c b/target/loongarch/tcg/csr_helper.c
index 46d331ce8a..28b1bb86bd 100644
--- a/target/loongarch/tcg/csr_helper.c
+++ b/target/loongarch/tcg/csr_helper.c
@@ -29,7 +29,11 @@ target_ulong helper_csrwr_stlbps(CPULoongArchState *env, target_ulong val)
     if (!check_ps(env, tlb_ps)) {
         qemu_log_mask(LOG_GUEST_ERROR,
                       "Attempted set ps %d\n", tlb_ps);
+    } else {
+        /* Only update PS field, reserved bit keeps zero */
+        env->CSR_STLBPS = FIELD_DP64(old_v, CSR_STLBPS, PS, tlb_ps);
     }
+
     return old_v;
 }