diff --git a/packages/payload/src/fields/validations.ts b/packages/payload/src/fields/validations.ts
index 8e13b70afc2..c03d2aee66c 100644
--- a/packages/payload/src/fields/validations.ts
+++ b/packages/payload/src/fields/validations.ts
@@ -166,7 +166,7 @@ export const email: EmailFieldValidation = (
   {
     collectionSlug,
     req: {
-      payload: { collections },
+      payload: { collections, config },
       t,
     },
     required,
@@ -174,7 +174,9 @@ export const email: EmailFieldValidation = (
   },
 ) => {
   if (collectionSlug) {
-    const collection = collections?.[collectionSlug]?.config
+    const collection =
+      collections?.[collectionSlug]?.config ??
+      config.collections.find(({ slug }) => slug === collectionSlug) // If this is run on the client, `collections` will be undefined, but `config.collections` will be available
 
     if (
       collection.auth.loginWithUsername &&
@@ -211,7 +213,9 @@ export const username: UsernameFieldValidation = (
   let maxLength: number
 
   if (collectionSlug) {
-    const collection = collections?.[collectionSlug]?.config
+    const collection =
+      collections?.[collectionSlug]?.config ??
+      config.collections.find(({ slug }) => slug === collectionSlug) // If this is run on the client, `collections` will be undefined, but `config.collections` will be available
 
     if (
       collection.auth.loginWithUsername &&