diff --git a/src/server.h b/src/server.h
index dd987ec2..c075fad4 100644
--- a/src/server.h
+++ b/src/server.h
@@ -339,7 +339,7 @@ typedef long long mstime_t; /* millisecond time type. */
 /* Anti-warning macro... */
 #define UNUSED(V) ((void) V)
 
-#define ZSKIPLIST_MAXLEVEL 32 /* Should be enough for 2^32 elements */
+#define ZSKIPLIST_MAXLEVEL 64 /* Should be enough for 2^64 elements */
 #define ZSKIPLIST_P 0.25      /* Skiplist P = 1/4 */
 
 /* Append only defines */
@@ -780,7 +780,7 @@ typedef struct zskiplistNode {
     struct zskiplistNode *backward;
     struct zskiplistLevel {
         struct zskiplistNode *forward;
-        unsigned int span;
+        unsigned long span;
     } level[];
 } zskiplistNode;