diff --git a/src/AttributedString.php b/src/AttributedString.php
index cd8d403..33b8200 100644
--- a/src/AttributedString.php
+++ b/src/AttributedString.php
@@ -11,7 +11,7 @@
 class AttributedString implements \Countable, \ArrayAccess
 {
   protected $string;
-  protected $attributes;
+  protected $attributes = [];
   protected $length;
   protected $byteToChar;
   
diff --git a/src/MutableAttributedString.php b/src/MutableAttributedString.php
index f3c6b74..6f144c0 100644
--- a/src/MutableAttributedString.php
+++ b/src/MutableAttributedString.php
@@ -51,8 +51,8 @@ public function insert($pos, $string) {
    */
   public function delete($pos, $length) {
     $leftPart = "";
-    if ($pos > 0) {
-      $leftPart = mb_substr($this->string, 0, $pos - 1, "utf-8");
+    if ($pos >= 0) {
+      $leftPart = mb_substr($this->string, 0, $pos, "utf-8");
     }
     
     $rightPart = "";
@@ -113,4 +113,24 @@ protected static function mb_substr_replace($string, $replacement, $start, $leng
     
     return join($smatches[0]);
   }
+  
+  // Modified ArrayAccess interface
+  
+  /**
+   * Replace char at given offset
+   *
+   * @param int $offset offset
+   */
+  public function offsetSet($offset, $value) {
+    $this->string = self::mb_substr_replace($this->string, $value, $offset, mb_strlen($value, "utf-8"));
+  }
+  
+  /**
+   * Unset char at given offset
+   *
+   * @param int $offset offset
+   */
+  public function offsetUnset($offset) {
+    $this->delete($offset, 1);
+  }
 }
diff --git a/test/unit/MutableAttributedStringTest.php b/test/unit/MutableAttributedStringTest.php
index 510f9e2..c514eef 100644
--- a/test/unit/MutableAttributedStringTest.php
+++ b/test/unit/MutableAttributedStringTest.php
@@ -31,7 +31,7 @@ public function testDelete() {
 
     $as->setLength(0, 11, "bold");
     $as->delete(4, 3);
-    $this->assertEquals("föö baz", $as);
+    $this->assertEquals("föö  baz", (string) $as);
     $this->assertEquals(true, $as->is("bold", 0), "start should still be bold");
     $this->assertEquals(true, $as->is("bold", 6), "end should still be bold");
 
@@ -48,9 +48,20 @@ public function testDelete() {
     $as = new MutableAttributedString("foo bar baz");
 
     $as->setLength(0, 11, "bold");
-    $as->delete(8, 4);
+    $as->delete(7, 4);
     $this->assertEquals("foo bar", $as);
     $this->assertEquals(true, $as->is("bold", 0), "start should still be bold");
     $this->assertEquals(true, $as->is("bold", 6), "end should still be bold");
   }
+  
+  public function testArrayAccess() {
+    $as = new MutableAttributedString("fóò bar bäz");
+    
+    $as[1] = "ö";
+    $this->assertEquals("ö", $as[1]);
+    $this->assertEquals("föò bar bäz", (string) $as);
+    
+    unset($as[1]);
+    $this->assertEquals("fò bar bäz", (string) $as);
+  }
 }