diff --git a/src/system/version_migration/versions/v1_0_4.ts b/src/system/version_migration/versions/v1_0_4.ts
index f16b6bcb6bb..d3b00ba0cae 100644
--- a/src/system/version_migration/versions/v1_0_4.ts
+++ b/src/system/version_migration/versions/v1_0_4.ts
@@ -1,6 +1,7 @@
 import { SettingKeys } from "../../settings/settings";
 import { AbilityAttr, defaultStarterSpecies, DexAttr, SystemSaveData, SessionSaveData  } from "../../game-data";
 import { allSpecies } from "../../../data/pokemon-species";
+import { CustomPokemonData } from "#app/data/custom-pokemon-data";
 
 export const systemMigrators = [
   /**
@@ -131,5 +132,28 @@ export const sessionMigrators = [
         m.className = "ResetNegativeStatStageModifier";
       }
     });
+  },
+  /**
+   *  Converts old Pokemon natureOverride and mysteryEncounterData
+   *  to use the new conjoined {@linkcode Pokemon.customPokemonData} structure instead.
+   *  @param data {@linkcode SessionSaveData}
+   */
+  function migrateCustomPokemonDataAndNatureOverrides(data: SessionSaveData) {
+    // Fix Pokemon nature overrides and custom data migration
+    data.party.forEach(pokemon => {
+      if (pokemon["mysteryEncounterPokemonData"]) {
+        pokemon.customPokemonData = new CustomPokemonData(pokemon["mysteryEncounterPokemonData"]);
+        pokemon["mysteryEncounterPokemonData"] = null;
+      }
+      if (pokemon["fusionMysteryEncounterPokemonData"]) {
+        pokemon.fusionCustomPokemonData = new CustomPokemonData(pokemon["fusionMysteryEncounterPokemonData"]);
+        pokemon["fusionMysteryEncounterPokemonData"] = null;
+      }
+      pokemon.customPokemonData = pokemon.customPokemonData ?? new CustomPokemonData();
+      if (pokemon["natureOverride"] && pokemon["natureOverride"] >= 0) {
+        pokemon.customPokemonData.nature = pokemon["natureOverride"];
+        pokemon["natureOverride"] = -1;
+      }
+    });
   }
 ] as const;
diff --git a/src/system/version_migration/versions/v1_1_0.ts b/src/system/version_migration/versions/v1_1_0.ts
index aac554c4531..5d6247aeaa2 100644
--- a/src/system/version_migration/versions/v1_1_0.ts
+++ b/src/system/version_migration/versions/v1_1_0.ts
@@ -1,32 +1,5 @@
-import { SessionSaveData } from "../../game-data";
-import { CustomPokemonData } from "#app/data/custom-pokemon-data";
-
 export const systemMigrators = [] as const;
 
 export const settingsMigrators = [] as const;
 
-export const sessionMigrators = [
-  /**
-   *  Converts old Pokemon natureOverride and mysteryEncounterData
-   *  to use the new conjoined {@linkcode Pokemon.customPokemonData} structure instead.
-   *  @param data {@linkcode SessionSaveData}
-   */
-  function migrateCustomPokemonDataAndNatureOverrides(data: SessionSaveData) {
-    // Fix Pokemon nature overrides and custom data migration
-    data.party.forEach(pokemon => {
-      if (pokemon["mysteryEncounterPokemonData"]) {
-        pokemon.customPokemonData = new CustomPokemonData(pokemon["mysteryEncounterPokemonData"]);
-        pokemon["mysteryEncounterPokemonData"] = null;
-      }
-      if (pokemon["fusionMysteryEncounterPokemonData"]) {
-        pokemon.fusionCustomPokemonData = new CustomPokemonData(pokemon["fusionMysteryEncounterPokemonData"]);
-        pokemon["fusionMysteryEncounterPokemonData"] = null;
-      }
-      pokemon.customPokemonData = pokemon.customPokemonData ?? new CustomPokemonData();
-      if (pokemon["natureOverride"] && pokemon["natureOverride"] >= 0) {
-        pokemon.customPokemonData.nature = pokemon["natureOverride"];
-        pokemon["natureOverride"] = -1;
-      }
-    });
-  }
-] as const;
+export const sessionMigrators = [] as const;