diff --git a/packages/backend/src/core/ReactionService.ts b/packages/backend/src/core/ReactionService.ts
index edf433025d..f3f2b04dd6 100644
--- a/packages/backend/src/core/ReactionService.ts
+++ b/packages/backend/src/core/ReactionService.ts
@@ -188,7 +188,7 @@ export class ReactionService {
 			.set({
 				reactions: () => sql,
 				...(note.reactionAndUserPairCache.length < 10 ? {
-					reactionAndUserPairCache: () => `array_append("reactionAndUserPairCache", '${user.id}:${reaction}')`,
+					reactionAndUserPairCache: () => `array_append("reactionAndUserPairCache", '${user.id}/${reaction}')`,
 				} : {}),
 			})
 			.where('id = :id', { id: note.id })
@@ -296,7 +296,7 @@ export class ReactionService {
 		await this.notesRepository.createQueryBuilder().update()
 			.set({
 				reactions: () => sql,
-				reactionAndUserPairCache: () => `array_remove("reactionAndUserPairCache", '${user.id}:${exist.reaction}')`,
+				reactionAndUserPairCache: () => `array_remove("reactionAndUserPairCache", '${user.id}/${exist.reaction}')`,
 			})
 			.where('id = :id', { id: note.id })
 			.execute();
diff --git a/packages/backend/src/core/entities/NoteEntityService.ts b/packages/backend/src/core/entities/NoteEntityService.ts
index b46b5528a5..c100b92ee7 100644
--- a/packages/backend/src/core/entities/NoteEntityService.ts
+++ b/packages/backend/src/core/entities/NoteEntityService.ts
@@ -187,7 +187,7 @@ export class NoteEntityService implements OnModuleInit {
 		if (note.reactionAndUserPairCache && reactionsCount <= note.reactionAndUserPairCache.length) {
 			const pair = note.reactionAndUserPairCache.find(p => p.startsWith(meId));
 			if (pair) {
-				return this.reactionService.convertLegacyReaction(pair.split(':')[1]);
+				return this.reactionService.convertLegacyReaction(pair.split('/')[1]);
 			} else {
 				return undefined;
 			}
@@ -411,7 +411,7 @@ export class NoteEntityService implements OnModuleInit {
 						myReactionsMap.set(note.renote.id, null);
 					} else if (reactionsCount <= note.renote.reactionAndUserPairCache.length) {
 						const pair = note.renote.reactionAndUserPairCache.find(p => p.startsWith(meId));
-						myReactionsMap.set(note.renote.id, pair ? pair.split(':')[1] : null);
+						myReactionsMap.set(note.renote.id, pair ? pair.split('/')[1] : null);
 					} else {
 						idsNeedFetchMyReaction.add(note.renote.id);
 					}
@@ -422,7 +422,7 @@ export class NoteEntityService implements OnModuleInit {
 							myReactionsMap.set(note.id, null);
 						} else if (reactionsCount <= note.reactionAndUserPairCache.length) {
 							const pair = note.reactionAndUserPairCache.find(p => p.startsWith(meId));
-							myReactionsMap.set(note.id, pair ? pair.split(':')[1] : null);
+							myReactionsMap.set(note.id, pair ? pair.split('/')[1] : null);
 						} else {
 							idsNeedFetchMyReaction.add(note.id);
 						}