diff --git a/src/pokemon_3.c b/src/pokemon_3.c
index 48986b1f0..a42ebf95d 100644
--- a/src/pokemon_3.c
+++ b/src/pokemon_3.c
@@ -189,7 +189,7 @@ s16 GetBaseSpecies(s16 index) {
 }
 
 s16 GetBaseSpeciesNoUnown(s16 index) {
-    register s32 a1_ asm("r2") = index;
+    s32 a1_ = SpeciesId(index);
     if (index == MONSTER_CASTFORM_SNOWY) {
         return MONSTER_CASTFORM;
     }