diff --git a/src/Google/Spreadsheet/Sheet.php b/src/Google/Spreadsheet/Sheet.php
index 0dfc549..f72badd 100644
--- a/src/Google/Spreadsheet/Sheet.php
+++ b/src/Google/Spreadsheet/Sheet.php
@@ -141,7 +141,7 @@ private function process($entry){
 				continue;
 			}
 			if($this->fields[$c]){
-				$this->items[$r] = is_array($this->items[$r]) ? $this->items[$r] : array();
+				$this->items[$r] = isset($this->items[$r]) && is_array($this->items[$r]) ? $this->items[$r] : array();
 				$this->items[$r][$this->fields[$c]] = $content;
 			}
 		}