diff --git a/include/hw/registerfields.h b/include/hw/registerfields.h
index 9a03ac55e4..f2a3c9c41f 100644
--- a/include/hw/registerfields.h
+++ b/include/hw/registerfields.h
@@ -95,7 +95,7 @@
     _d; })
 #define FIELD_DP64(storage, reg, field, val) ({                           \
     struct {                                                              \
-        unsigned int v:R_ ## reg ## _ ## field ## _LENGTH;                \
+        uint64_t v:R_ ## reg ## _ ## field ## _LENGTH;                \
     } _v = { .v = val };                                                  \
     uint64_t _d;                                                          \
     _d = deposit64((storage), R_ ## reg ## _ ## field ## _SHIFT,          \