diff --git a/lib/node.js b/lib/node.js
index 6ece68d..d25b844 100644
--- a/lib/node.js
+++ b/lib/node.js
@@ -265,6 +265,8 @@ Node.prototype.calculateBlockTimes = function()
 	{
 		var diff = (key > 0 ? list[key - 1].timestamp : Math.floor(Date.now()/1000)) - block.timestamp;
 
+		diff = Math.max(diff, 0);
+
 		return diff;
 	});