diff --git a/drivers/reg.h b/drivers/reg.h
index 05cdc19..5334e18 100644
--- a/drivers/reg.h
+++ b/drivers/reg.h
@@ -7,7 +7,7 @@
 #define reg_reset(reg, field) _reg_reset(reg, field)
 #define _reg_reset(reg, pos, mask) do { reg.word &= ~mask; } while (false)
 
-#define reg_write(reg, field, value) _reg_write(reg, field, value)
+#define reg_write(reg, field, value) _reg_write(reg, field, (value))
 #define _reg_write(reg, pos, mask, value) \
 do {                                      \
 	reg.word |= value << pos;             \