2 files changed, 8 insertions, 2 deletions
diff --git a/src/background/infrastructures/memory-storage.js b/src/background/infrastructures/memory-storage.js
index 234a9b8..3a7e4f2 100644
--- a/src/background/infrastructures/memory-storage.js
+++ b/src/background/infrastructures/memory-storage.js
@@ -10,6 +10,10 @@ export default class MemoryStorage {
   }
 
   get(name) {
-    return JSON.parse(db[name]);
+    let data = db[name];
+    if (!data) {
+      return undefined;
+    }
+    return JSON.parse(data);
   }
 }
diff --git a/src/background/usecases/operation.js b/src/background/usecases/operation.js
index f19c632..86f39ca 100644
--- a/src/background/usecases/operation.js
+++ b/src/background/usecases/operation.js
@@ -183,7 +183,9 @@ export default class OperationInteractor {
 
   onTabSelected(tabId) {
     let lastId = this.cache.get(CURRENT_SELECTED_KEY);
-    this.cache.set(LAST_SELECTED_KEY, lastId);
+    if (lastId) {
+      this.cache.set(LAST_SELECTED_KEY, lastId);
+    }
     this.cache.set(CURRENT_SELECTED_KEY, tabId);
   }
 }