diff --git a/lib/timeutils/timeutils.c b/lib/timeutils/timeutils.c
index 518f570090..c897131c65 100644
--- a/lib/timeutils/timeutils.c
+++ b/lib/timeutils/timeutils.c
@@ -158,8 +158,8 @@ mp_uint_t timeutils_seconds_since_2000(mp_uint_t year, mp_uint_t month,
         + (year - 2000) * 31536000;
 }
 
-mp_uint_t timeutils_mktime(mp_uint_t year, mp_uint_t month, mp_uint_t mday,
-    mp_uint_t hours, mp_uint_t minutes, mp_uint_t seconds) {
+mp_uint_t timeutils_mktime(mp_uint_t year, mp_int_t month, mp_int_t mday,
+    mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {
 
     // Normalize the tuple. This allows things like:
     //
diff --git a/lib/timeutils/timeutils.h b/lib/timeutils/timeutils.h
index d6e3536ad7..c3f1fc2db1 100644
--- a/lib/timeutils/timeutils.h
+++ b/lib/timeutils/timeutils.h
@@ -49,7 +49,7 @@ void timeutils_seconds_since_2000_to_struct_time(mp_uint_t t,
 mp_uint_t timeutils_seconds_since_2000(mp_uint_t year, mp_uint_t month,
     mp_uint_t date, mp_uint_t hour, mp_uint_t minute, mp_uint_t second);
 
-mp_uint_t timeutils_mktime(mp_uint_t year, mp_uint_t month, mp_uint_t mday,
-    mp_uint_t hours, mp_uint_t minutes, mp_uint_t seconds);
+mp_uint_t timeutils_mktime(mp_uint_t year, mp_int_t month, mp_int_t mday,
+    mp_int_t hours, mp_int_t minutes, mp_int_t seconds);
 
 #endif // __MICROPY_INCLUDED_LIB_TIMEUTILS_H__