diff --git a/stm8s.h b/stm8s.h
index 831de09..5273390 100644
--- a/stm8s.h
+++ b/stm8s.h
@@ -1058,6 +1058,8 @@ typedef struct {
 #define I2C_ITR_ITBUFEN (1 << 2)
 #define I2C_CCRL (*(volatile uint8_t *)(I2C_BASE + 0x0B))
 #define I2C_CCRH (*(volatile uint8_t *)(I2C_BASE + 0x0C))
+#define I2C_CCRH_DUTY (1U << 6)
+#define I2C_CCRH_FS (1U << 7)
 #define I2C_TRISER (*(volatile uint8_t *)(I2C_BASE + 0x0D))
 #define I2C_PECR (*(volatile uint8_t *)(I2C_BASE + 0x0E))