diff --git a/src/phases/learn-move-phase.ts b/src/phases/learn-move-phase.ts
index 201019e8860..6f0f63ef106 100644
--- a/src/phases/learn-move-phase.ts
+++ b/src/phases/learn-move-phase.ts
@@ -44,6 +44,7 @@ export class LearnMovePhase extends PlayerPartyMemberPokemonPhase {
     if (emptyMoveIndex > -1) {
       pokemon.setMove(emptyMoveIndex, this.moveId);
       if (this.fromTM) {
+        pokemon.usedTMs ??= [];
         pokemon.usedTMs.push(this.moveId);
       }
       initMoveAnim(this.scene, this.moveId).then(() => {