diff --git a/src/battle_util.c b/src/battle_util.c
index 42329b5495..617bb8b2e5 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -11248,6 +11248,8 @@ void SetShellSideArmCategory(void)
             statStage = gBattleMons[battlerDef].statStages[STAT_DEF];
             targetDefStat *= gStatStageRatios[statStage][0];
             targetDefStat /= gStatStageRatios[statStage][1];
+            if (targetDefStat == 0)
+                targetDefStat = 1;
 
             physical = ((((2 * gBattleMons[battlerAtk].level / 5 + 2) * power * attackerAtkStat) / targetDefStat) / 50);
 
@@ -11255,6 +11257,8 @@ void SetShellSideArmCategory(void)
             statStage = gBattleMons[battlerDef].statStages[STAT_SPDEF];
             targetSpDefStat *= gStatStageRatios[statStage][0];
             targetSpDefStat /= gStatStageRatios[statStage][1];
+            if (targetSpDefStat == 0)
+                targetSpDefStat = 1;
 
             special = ((((2 * gBattleMons[battlerAtk].level / 5 + 2) * power * attackerSpAtkStat) / targetSpDefStat) / 50);