diff --git a/jetty-http/src/main/java/org/eclipse/jetty/http/HttpFields.java b/jetty-http/src/main/java/org/eclipse/jetty/http/HttpFields.java
index dbd1eecaa76f..7bf249f22064 100644
--- a/jetty-http/src/main/java/org/eclipse/jetty/http/HttpFields.java
+++ b/jetty-http/src/main/java/org/eclipse/jetty/http/HttpFields.java
@@ -639,14 +639,14 @@ public Mutable add(HttpField field)
 
         public Mutable add(HttpFields fields)
         {
-            if (fields.size() == 0)
-                return this;
-
             if (_fields == null)
                 _fields = new HttpField[fields.size() + 4];
             else if (_size + fields.size() >= _fields.length)
                 _fields = Arrays.copyOf(_fields, _size + fields.size() + 4);
 
+            if (fields.size() == 0)
+                return this;
+
             if (fields instanceof Immutable)
             {
                 Immutable b = (Immutable)fields;
diff --git a/jetty-http/src/test/java/org/eclipse/jetty/http/HttpFieldsTest.java b/jetty-http/src/test/java/org/eclipse/jetty/http/HttpFieldsTest.java
index be2e871d40b1..04ebd3905d25 100644
--- a/jetty-http/src/test/java/org/eclipse/jetty/http/HttpFieldsTest.java
+++ b/jetty-http/src/test/java/org/eclipse/jetty/http/HttpFieldsTest.java
@@ -745,7 +745,7 @@ public void testAddNullName()
     @Test
     public void testAddHttpFields()
     {
-        HttpFields.Mutable fields = HttpFields.build();
+        HttpFields.Mutable fields = new HttpFields.Mutable(new HttpFields.Mutable());
         fields.add("One", "1");
 
         fields = new HttpFields.Mutable(fields);