diff --git a/data/battle_scripts_1.s b/data/battle_scripts_1.s
index d20a5e4f6e..f24047f115 100644
--- a/data/battle_scripts_1.s
+++ b/data/battle_scripts_1.s
@@ -5050,7 +5050,7 @@ BattleScript_EffectBatonPass::
 	goto BattleScript_MoveEnd
 
 BattleScript_EffectRapidSpin::
-.if B_SPEED_BUFFING_RAPID_SPIN == GEN_8
+.if B_SPEED_BUFFING_RAPID_SPIN >= GEN_8
 	call BattleScript_EffectHit_Ret
 	jumpifhalfword CMP_COMMON_BITS, gMoveResultFlags, MOVE_RESULT_DOESNT_AFFECT_FOE, BattleScript_MoveEnd
 	setmoveeffect MOVE_EFFECT_RAPIDSPIN | MOVE_EFFECT_AFFECTS_USER | MOVE_EFFECT_CERTAIN
diff --git a/src/battle_interface.c b/src/battle_interface.c
index 7ac936b2f7..a087c715b7 100644
--- a/src/battle_interface.c
+++ b/src/battle_interface.c
@@ -1409,11 +1409,10 @@ bool32 IsMegaTriggerSpriteActive(void)
 
 void HideMegaTriggerSprite(void)
 {
-    if (gBattleStruct->mega.triggerSpriteId != 0xFF)
-    {
-        ChangeMegaTriggerSprite(gBattleStruct->mega.triggerSpriteId, 0);
-        gSprites[gBattleStruct->mega.triggerSpriteId].tHide = TRUE;
-    }
+    if (gBattleStruct->mega.triggerSpriteId >= MAX_SPRITES)
+        return;
+    ChangeMegaTriggerSprite(gBattleStruct->mega.triggerSpriteId, 0);
+    gSprites[gBattleStruct->mega.triggerSpriteId].tHide = TRUE;
 }
 
 void HideTriggerSprites(void)
diff --git a/src/battle_util.c b/src/battle_util.c
index 46014e3936..c15c46a092 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -10141,14 +10141,14 @@ bool32 CanMegaEvolve(u8 battlerId)
     species = GetMonData(mon, MON_DATA_SPECIES);
     itemId = GetMonData(mon, MON_DATA_HELD_ITEM);
 
+    if (itemId == ITEM_ENIGMA_BERRY_E_READER)
+        holdEffect = gEnigmaBerries[battlerId].holdEffect;
+    else
+        holdEffect = ItemId_GetHoldEffect(itemId);
+
     // Check if there is an entry in the evolution table for regular Mega Evolution.
     if (GetBattleFormChangeTargetSpecies(battlerId, FORM_CHANGE_BATTLE_MEGA_EVOLUTION_ITEM) != SPECIES_NONE)
     {
-        if (itemId == ITEM_ENIGMA_BERRY_E_READER)
-            holdEffect = gEnigmaBerries[battlerId].holdEffect;
-        else
-            holdEffect = ItemId_GetHoldEffect(itemId);
-
         // Can Mega Evolve via Mega Stone.
         if (holdEffect == HOLD_EFFECT_MEGA_STONE)
             return TRUE;
@@ -10156,7 +10156,11 @@ bool32 CanMegaEvolve(u8 battlerId)
 
     // Check if there is an entry in the evolution table for Wish Mega Evolution.
     if (GetBattleFormChangeTargetSpecies(battlerId, FORM_CHANGE_BATTLE_MEGA_EVOLUTION_MOVE) != SPECIES_NONE)
-        return TRUE;
+    {
+        // Can't Wish Mega Evolve if holding a Z Crystal.
+        if (holdEffect != HOLD_EFFECT_Z_CRYSTAL)
+            return TRUE;
+    }
 
     // No checks passed, the mon CAN'T mega evolve.
     return FALSE;
diff --git a/src/battle_z_move.c b/src/battle_z_move.c
index 55cc157bee..3983f96b94 100644
--- a/src/battle_z_move.c
+++ b/src/battle_z_move.c
@@ -159,7 +159,6 @@ void QueueZMove(u8 battlerId, u16 baseMove)
 bool32 IsViableZMove(u8 battlerId, u16 move)
 {
     struct Pokemon *mon;
-    struct MegaEvolutionData *mega = &(((struct ChooseMoveStruct *)(&gBattleResources->bufferA[gActiveBattler][4]))->mega);
     u8 battlerPosition = GetBattlerPosition(battlerId);
     u8 partnerPosition = GetBattlerPosition(BATTLE_PARTNER(battlerId));
     u32 item;
@@ -185,15 +184,6 @@ bool32 IsViableZMove(u8 battlerId, u16 move)
     if ((GetBattlerPosition(battlerId) == B_POSITION_PLAYER_LEFT || (!(gBattleTypeFlags & BATTLE_TYPE_MULTI) && GetBattlerPosition(battlerId) == B_POSITION_PLAYER_RIGHT)) && !CheckBagHasItem(ITEM_Z_POWER_RING, 1))
         return FALSE;
 
-    if (mega->alreadyEvolved[battlerPosition])
-        return FALSE;   // Trainer has mega evolved
-
-    if (gBattleTypeFlags & BATTLE_TYPE_DOUBLE)
-    {
-        if (IsPartnerMonFromSameTrainer(battlerId) && (mega->alreadyEvolved[partnerPosition] || (mega->toEvolve & gBitTable[BATTLE_PARTNER(battlerId)])))
-            return FALSE;   // Partner has mega evolved or is about to mega evolve
-    }
-
     if (item == ITEM_ENIGMA_BERRY_E_READER)
         return FALSE;   // HoldEffect = gEnigmaBerries[battlerId].holdEffect;
     else
@@ -350,9 +340,12 @@ bool32 IsZMoveTriggerSpriteActive(void)
 
 void HideZMoveTriggerSprite(void)
 {
-    struct Sprite *sprite = &gSprites[gBattleStruct->zmove.triggerSpriteId];
-    sprite->tHide = TRUE;
+    struct Sprite *sprite;
     gBattleStruct->zmove.viable = FALSE;
+    if (gBattleStruct->zmove.triggerSpriteId >= MAX_SPRITES)
+        return;
+    sprite = &gSprites[gBattleStruct->zmove.triggerSpriteId];
+    sprite->tHide = TRUE;
 }
 
 static void ShowZMoveTriggerSprite(u8 battlerId)
diff --git a/src/data/items.h b/src/data/items.h
index 802cd325da..5e15b27344 100644
--- a/src/data/items.h
+++ b/src/data/items.h
@@ -6,7 +6,7 @@
     #define EVO_HELD_ITEM_FIELD_FUNC ItemUseOutOfBattle_CannotUse
 #endif
 
-#if I_GEM_BOOST_POWER >= GEN_5
+#if I_GEM_BOOST_POWER >= GEN_6
     #define GEM_BOOST_PARAM 30
 #else
     #define GEM_BOOST_PARAM 50