diff --git a/src/main/java/org/apache/commons/lang3/builder/ReflectionToStringBuilder.java b/src/main/java/org/apache/commons/lang3/builder/ReflectionToStringBuilder.java
index b47049ca6..816206b6d 100644
--- a/src/main/java/org/apache/commons/lang3/builder/ReflectionToStringBuilder.java
+++ b/src/main/java/org/apache/commons/lang3/builder/ReflectionToStringBuilder.java
@@ -648,7 +648,8 @@ public class ReflectionToStringBuilder extends ToStringBuilder {
         if (excludeFieldNamesParam == null) {
             this.excludeFieldNames = null;
         } else {
-            this.excludeFieldNames = excludeFieldNamesParam.clone();
+            //clone and remove nulls
+            this.excludeFieldNames = toNoNullStringArray(excludeFieldNamesParam);
             Arrays.sort(this.excludeFieldNames);
         }
         return this;