diff --git a/libcpu/risc-v/common64/mmu.c b/libcpu/risc-v/common64/mmu.c
index badb7bebe63..6cab811eca7 100644
--- a/libcpu/risc-v/common64/mmu.c
+++ b/libcpu/risc-v/common64/mmu.c
@@ -648,6 +648,8 @@ void rt_hw_mmu_setup(rt_aspace_t aspace, struct mem_desc *mdesc, int desc_nr)
 
 #define SATP_BASE ((rt_ubase_t)SATP_MODE << SATP_MODE_OFFSET)
 
+extern unsigned int __bss_end;
+
 /**
  * @brief Early memory setup function for hardware initialization.
  *