diff --git a/website/server/controllers/api-v3/hall.js b/website/server/controllers/api-v3/hall.js
index 6948a0c133..dd415eeb5e 100644
--- a/website/server/controllers/api-v3/hall.js
+++ b/website/server/controllers/api-v3/hall.js
@@ -479,7 +479,7 @@ api.updateHero = {
       }
 
       if (updateData.auth.local && updateData.auth.local.email) {
-        hero.auth.local.email = updateData.auth.local.email;
+        hero.auth.local.email = updateData.auth.local.email.toLowerCase();
       }
     }
 
diff --git a/website/server/libs/auth/social.js b/website/server/libs/auth/social.js
index b9ce82c194..1677192c1f 100644
--- a/website/server/libs/auth/social.js
+++ b/website/server/libs/auth/social.js
@@ -33,7 +33,7 @@ export async function socialEmailToLocal (user) {
       { 'auth.local.email': socialEmail },
       { _id: 1 },
     ).exec();
-    if (!conflictingUser) return socialEmail;
+    if (!conflictingUser) return socialEmail.toLowerCase();
   }
   return undefined;
 }