diff --git a/src/main/java/cpw/mods/fml/common/registry/GameData.java b/src/main/java/cpw/mods/fml/common/registry/GameData.java
index c7a3c93..4924424 100644
--- a/src/main/java/cpw/mods/fml/common/registry/GameData.java
+++ b/src/main/java/cpw/mods/fml/common/registry/GameData.java
@@ -677,8 +677,8 @@
 
 			try
 			{
-				String skip = System.getProperty("fml.doNotBackup");
-				if (skip == null || !"true".equals(skip))
+				String dob = System.getProperty("fml.doBackup");
+				if (dob != null && "true".equals(dob))
 				{
 					ZipperUtil.backupWorld();
 				}