diff --git a/src/background/index.js b/src/background/index.js
index 4aa3856..8913a83 100644
--- a/src/background/index.js
+++ b/src/background/index.js
@@ -99,7 +99,5 @@ browser.runtime.onMessage.addListener((request, sender) => {
         items: items
       };
     });
-    break;
   }
-  return Promise.resolve();
 });
diff --git a/src/content/index.js b/src/content/index.js
index e682a7f..fdc7e89 100644
--- a/src/content/index.js
+++ b/src/content/index.js
@@ -97,9 +97,9 @@ const doCompletion = (line) => {
       text: keyword
     }).then((completions) => {
       vvConsole.setCompletions([completions]);
-    }).catch((e) => {
+    }).catch((err) => {
       console.error("Vim Vixen:", err);
-      vvConsole.showError(e.message);
+      vvConsole.showError(err.message);
     });
   }
 };
@@ -115,9 +115,9 @@ messages.receive(window, (message) => {
     browser.runtime.sendMessage({
       type: 'event.cmd.enter',
       text: message.value
-    }).catch((e) => {
+    }).catch((err) => {
       console.error("Vim Vixen:", err);
-      vvConsole.showError(e.message);
+      vvConsole.showError(err.message);
     });
     break;
   case 'vimvixen.command.change':