diff --git a/VERSION b/VERSION
index 7849b73..8ac3c44 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-6.3.3
+6.3.4
diff --git a/composer.json b/composer.json
index f921ee4..839f60b 100644
--- a/composer.json
+++ b/composer.json
@@ -1,6 +1,6 @@
 {
   "name": "tecnickcom/tcpdf",
-  "version": "6.3.3",
+  "version": "6.3.4",
   "homepage": "http://www.tcpdf.org/",
   "type": "library",
   "description": "TCPDF is a PHP class for generating PDF documents and barcodes.",
diff --git a/include/tcpdf_static.php b/include/tcpdf_static.php
index a1ff440..8e96869 100644
--- a/include/tcpdf_static.php
+++ b/include/tcpdf_static.php
@@ -55,7 +55,7 @@ class TCPDF_STATIC {
 	 * Current TCPDF version.
 	 * @private static
 	 */
-	private static $tcpdf_version = '6.3.3';
+	private static $tcpdf_version = '6.3.4';
 
 	/**
 	 * String alias for total number of pages.
diff --git a/tcpdf.php b/tcpdf.php
index 21dabe7..1ebea72 100644
--- a/tcpdf.php
+++ b/tcpdf.php
@@ -7785,8 +7785,10 @@ class TCPDF {
 				}
 				closedir($handle);
 			}
-			foreach($this->imagekeys as $file) {
-				unlink($file);
+			if (isset($this->imagekeys)) {
+				foreach($this->imagekeys as $file) {
+					unlink($file);
+				}
 			}
 		}
 		$preserve = array(