diff --git a/field.h b/field.h
index 01cadf763..7e74c9a76 100644
--- a/field.h
+++ b/field.h
@@ -126,10 +126,10 @@ struct field_effect {
 };
 struct field_info {
 	int32 field_id{ 1 };
-	int16 copy_id{ 1 };
-	int16 turn_id{};
-	int16 turn_id_by_player[2]{};
-	int16 card_id{ 1 };
+	uint16 copy_id{ 1 };
+	uint16 turn_id{};
+	uint16 turn_id_by_player[2]{};
+	uint16 card_id{ 1 };
 	uint16 phase{};
 	uint8 turn_player{};
 	uint8 priorities[2]{};