diff --git a/service/database/db-users.go b/service/database/db-users.go
index 3d0bd80..003e635 100644
--- a/service/database/db-users.go
+++ b/service/database/db-users.go
@@ -2,6 +2,7 @@ package database
 
 import (
 	"database/sql"
+	"errors"
 
 	"github.com/gofrs/uuid"
 	"github.com/notherealmarco/WASAPhoto/service/database/db_errors"
@@ -47,6 +48,16 @@ func (db *appdbimpl) GetUserID(name string) (string, error) {
 
 // Create a new user
 func (db *appdbimpl) CreateUser(name string) (string, error) {
+
+	// check if username is taken (case insensitive)
+	exists, err := db.nameExists(name)
+
+	if err != nil {
+		return "", err
+	} else if exists {
+		return "", errors.New("username already exists")
+	}
+
 	uid, err := uuid.NewV4()
 	if err != nil {
 		return "", err
@@ -55,14 +66,30 @@ func (db *appdbimpl) CreateUser(name string) (string, error) {
 	return uid.String(), err
 }
 
+// Check if username exists
+func (db *appdbimpl) nameExists(name string) (bool, error) {
+	var cnt int
+	err := db.c.QueryRow(`SELECT COUNT(*) FROM "users" WHERE "name" LIKE ?`, name).Scan(&cnt)
+	if err != nil {
+		return false, err
+	}
+	return cnt > 0, nil
+}
+
 // Update username
 func (db *appdbimpl) UpdateUsername(uid string, name string) (QueryResult, error) {
-	_, err := db.c.Exec(`UPDATE "users" SET "name" = ? WHERE "uid" = ?`, name, uid)
 
-	if db_errors.UniqueViolation(err) {
+	// check if username is taken (case insensitive)
+	exists, err := db.nameExists(name)
+
+	if err != nil {
+		return ERR_INTERNAL, err
+	} else if exists {
 		return ERR_EXISTS, nil
 	}
 
+	_, err = db.c.Exec(`UPDATE "users" SET "name" = ? WHERE "uid" = ?`, name, uid)
+
 	if err != nil {
 		return ERR_INTERNAL, err
 	}