diff --git a/services/src/main/java/org/keycloak/forms/login/freemarker/FreeMarkerLoginFormsProvider.java b/services/src/main/java/org/keycloak/forms/login/freemarker/FreeMarkerLoginFormsProvider.java
index 22a3569834..e43ca28aec 100755
--- a/services/src/main/java/org/keycloak/forms/login/freemarker/FreeMarkerLoginFormsProvider.java
+++ b/services/src/main/java/org/keycloak/forms/login/freemarker/FreeMarkerLoginFormsProvider.java
@@ -586,11 +586,19 @@ public class FreeMarkerLoginFormsProvider implements LoginFormsProvider {
     public Response createRegistration() {
         String loginHint = authenticationSession.getClientNote(OIDCLoginProtocol.LOGIN_HINT_PARAM);
         if (loginHint != null && !loginHint.isEmpty()) {
-            this.formData = new MultivaluedHashMap<>();
+            if (this.formData == null) {
+                this.formData = new MultivaluedHashMap<>();
+            }
             if(this.realm.isRegistrationEmailAsUsername()) {
-                this.formData.putSingle("email", loginHint);
+                String value = this.formData.getFirst("email");
+                if (value == null || value.trim().isEmpty()) {
+                    this.formData.putSingle("email", loginHint);
+                }
             } else {
-                this.formData.putSingle("username", loginHint);
+                String value = this.formData.getFirst("username");
+                if (value == null || value.trim().isEmpty()) {
+                    this.formData.putSingle("username", loginHint);
+                }
             }
         }