diff --git a/apc_iterator.c b/apc_iterator.c
index 07bd0e4e..eac7e5aa 100644
--- a/apc_iterator.c
+++ b/apc_iterator.c
@@ -316,7 +316,7 @@ static void apc_iterator_totals(apc_iterator_t *iterator) {
 }
 /* }}} */
 
-void apc_iterator_obj_init(apc_iterator_t *iterator, zval *search, zend_long format, size_t chunk_size, zend_long list)
+void apc_iterator_obj_init(apc_iterator_t *iterator, zval *search, zend_ulong format, size_t chunk_size, zend_long list)
 {
 	if (!APCG(enabled)) {
 		zend_throw_error(NULL, "APC must be enabled to use APCUIterator");
diff --git a/apc_iterator.h b/apc_iterator.h
index 9feda387..d49eae3f 100644
--- a/apc_iterator.h
+++ b/apc_iterator.h
@@ -49,7 +49,7 @@
 /* {{{ apc_iterator_t */
 typedef struct _apc_iterator_t {
 	short int initialized;   /* sanity check in case __construct failed */
-	zend_long format;             /* format bitmask of the return values ie: key, value, info */
+	zend_ulong format;       /* format bitmask of the return values ie: key, value, info */
 	size_t (*fetch)(struct _apc_iterator_t *iterator);
 							 /* fetch callback to fetch items from cache slots or lists */
 	size_t slot_idx;           /* index to the slot array or linked list */