diff --git a/lib/github-id-mapper.js b/lib/github-id-mapper.js
index 04ddd77..ea0598b 100644
--- a/lib/github-id-mapper.js
+++ b/lib/github-id-mapper.js
@@ -20,6 +20,9 @@ class GitHubSlackIdMapper {
     this.robot = robot
     this.cache = new MemCache({ timeoutDisabled: true })
     this.buildPromise = new Promise((resolve, reject) => internalBuild(this.robot, this.cache).then(resolve).catch(reject))
+
+    // Refresh cache every day
+    setTimeout(() => internalBuild(this.robot, this.cache), 24 * 60 * 60 * 1000)
   }
 
   async getGitHubIdFromSlackId (slackUserId, cache) {