diff --git a/src/flatcollections-array/FlatArray/FlatArray.T.Builder/FlatArray.Builder.AddRange.Array.cs b/src/flatcollections-array/FlatArray/FlatArray.T.Builder/FlatArray.Builder.AddRange.Array.cs
index da334e4a..b3b82ae3 100644
--- a/src/flatcollections-array/FlatArray/FlatArray.T.Builder/FlatArray.Builder.AddRange.Array.cs
+++ b/src/flatcollections-array/FlatArray/FlatArray.T.Builder/FlatArray.Builder.AddRange.Array.cs
@@ -15,7 +15,7 @@ internal Builder AddRange([AllowNull] params T[] items)
                 return this;
             }
 
-            InnerAddRange(items, items.Length);
+            InnerAddRange(items);
             return this;
         }
 
@@ -38,6 +38,14 @@ internal Builder AddRange([AllowNull] T[] items, int length)
             return this;
         }
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void InnerAddRange(T[] items)
+        {
+            InnerBufferHelperEx.EnsureBufferCapacity(ref this.items, length, items.Length);
+            new ReadOnlySpan<T>(items).CopyTo(new Span<T>(this.items, length, items.Length));
+            length += items.Length;
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private void InnerAddRange(T[] items, int length)
         {
diff --git a/src/flatcollections-array/FlatArray/FlatArray.T.Builder/FlatArray.Builder.AddRange.FlatArray.cs b/src/flatcollections-array/FlatArray/FlatArray.T.Builder/FlatArray.Builder.AddRange.FlatArray.cs
index 11cacee8..d7d4f16f 100644
--- a/src/flatcollections-array/FlatArray/FlatArray.T.Builder/FlatArray.Builder.AddRange.FlatArray.cs
+++ b/src/flatcollections-array/FlatArray/FlatArray.T.Builder/FlatArray.Builder.AddRange.FlatArray.cs
@@ -12,7 +12,7 @@ internal Builder AddRange(FlatArray<T> items)
                 return this;
             }
 
-            InnerAddRange(items, items.length);
+            InnerAddRange(items);
             return this;
         }