diff --git a/.changeset/wet-students-taste.md b/.changeset/wet-students-taste.md
new file mode 100644
index 00000000..0acd77b3
--- /dev/null
+++ b/.changeset/wet-students-taste.md
@@ -0,0 +1,5 @@
+---
+"sv": patch
+---
+
+fix: make `lucia` validation error messages more descriptive
diff --git a/packages/addons/lucia/index.ts b/packages/addons/lucia/index.ts
index ba5e19d6..d064c807 100644
--- a/packages/addons/lucia/index.ts
+++ b/packages/addons/lucia/index.ts
@@ -398,10 +398,10 @@ export default defineAddon({
 							const password = formData.get('password');
 
 							if (!validateUsername(username)) {
-								return fail(400, { message: 'Invalid username' });
+								return fail(400, { message: 'Invalid username (min 3, max 31 characters, alphanumeric only)' });
 							}
 							if (!validatePassword(password)) {
-								return fail(400, { message: 'Invalid password' });
+								return fail(400, { message: 'Invalid password (min 6, max 255 characters)' });
 							}
 
 							const results = await db