diff --git a/target/riscv/gdbstub.c b/target/riscv/gdbstub.c
index 27be93279b..ded140e8d8 100644
--- a/target/riscv/gdbstub.c
+++ b/target/riscv/gdbstub.c
@@ -313,7 +313,8 @@ static int riscv_gdb_get_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
          * register 33, so we recalculate the map index.
          * This also works for CSR_FRM and CSR_FCSR.
          */
-        result = riscv_csrrw_debug(env, n - 33 +  8, &val, 0, 0);
+        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], &val,
+                                   0, 0);
         if (result == 0) {
             return gdb_get_regl(mem_buf, val);
         }
@@ -335,7 +336,8 @@ static int riscv_gdb_set_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
          * register 33, so we recalculate the map index.
          * This also works for CSR_FRM and CSR_FCSR.
          */
-        result = riscv_csrrw_debug(env, n - 33 + 8, NULL, val, -1);
+        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], NULL,
+                                   val, -1);
         if (result == 0) {
             return sizeof(target_ulong);
         }