diff --git a/src/wp-admin/includes/file.php b/src/wp-admin/includes/file.php
index 5cb0f49211..4033a30cd7 100644
--- a/src/wp-admin/includes/file.php
+++ b/src/wp-admin/includes/file.php
@@ -258,8 +258,9 @@ function wp_handle_upload( &$file, $overrides = false, $time = null ) {
 		return call_user_func($upload_error_handler, $file, __( 'Invalid form submission.' ));
 
 	// A successful upload will pass this test. It makes no sense to override this one.
-	if ( $file['error'] > 0 )
-		return call_user_func($upload_error_handler, $file, $upload_error_strings[$file['error']] );
+	if ( isset( $file['error'] ) && $file['error'] > 0 ) {
+		return call_user_func( $upload_error_handler, $file, $upload_error_strings[ $file['error'] ] );
+	}
 
 	// A non-empty file will pass this test.
 	if ( $test_size && !($file['size'] > 0 ) ) {