diff --git a/src/gd32e23x_it.c b/src/gd32e23x_it.c
index b0c38fe..959897c 100644
--- a/src/gd32e23x_it.c
+++ b/src/gd32e23x_it.c
@@ -35,6 +35,9 @@ OF SUCH DAMAGE.
 #include "gd32e23x_it.h"
 #include "main.h"
 #include "systick.h"
+#include "ultrasonic_driver.h"
+
+__IO uint32_t capture_value;
 
 /*!
     \brief      this function handles NMI exception