diff --git a/core/src/main/java/org/springframework/security/core/userdetails/User.java b/core/src/main/java/org/springframework/security/core/userdetails/User.java
index 461e2b478d1..2db66f3afe2 100644
--- a/core/src/main/java/org/springframework/security/core/userdetails/User.java
+++ b/core/src/main/java/org/springframework/security/core/userdetails/User.java
@@ -441,7 +441,7 @@ public UserBuilder authorities(GrantedAuthority... authorities) {
 		 */
 		public UserBuilder authorities(Collection<? extends GrantedAuthority> authorities) {
 			Assert.notNull(authorities, "authorities cannot be null");
-			this.authorities = new ArrayList<>(authorities);
+			this.authorities.addAll(authorities);
 			return this;
 		}