diff --git a/libcpu/risc-v/t-head/c906/trap.c b/libcpu/risc-v/t-head/c906/trap.c
index ac04fdbfa4..025b2d3092 100644
--- a/libcpu/risc-v/t-head/c906/trap.c
+++ b/libcpu/risc-v/t-head/c906/trap.c
@@ -28,6 +28,7 @@
 
 #ifdef RT_USING_SMART
 #include <lwp_arch.h>
+void rt_hw_backtrace(rt_uint32_t *ffp, rt_ubase_t sepc);
 #else
 #define rt_hw_backtrace(...) (0)
 #endif