diff --git a/src/k_kart.h b/src/k_kart.h
index db00d8841..9535ef7bb 100644
--- a/src/k_kart.h
+++ b/src/k_kart.h
@@ -22,7 +22,7 @@ void K_RegisterKartStuff(void);
 
 boolean K_IsPlayerLosing(player_t *player);
 boolean K_IsPlayerWanted(player_t *player);
-fixed_t K_GetKartGameSpeedScalar(UINT8 value);
+fixed_t K_GetKartGameSpeedScalar(SINT8 value);
 void K_KartBouncing(mobj_t *mobj1, mobj_t *mobj2, boolean bounce, boolean solid);
 void K_KartPainEnergyFling(player_t *player);
 void K_FlipFromObject(mobj_t *mo, mobj_t *master);