diff --git a/src/com/sheepit/client/standalone/Worker.java b/src/com/sheepit/client/standalone/Worker.java
index 7679f61..d4361a1 100644
--- a/src/com/sheepit/client/standalone/Worker.java
+++ b/src/com/sheepit/client/standalone/Worker.java
@@ -183,7 +183,7 @@ public class Worker {
 			}
 		}
 		
-		if (nb_cores < -1) {
+		if (nb_cores < -1 || nb_cores == 0) { // -1 is the default
 			System.err.println("Error: use-number-core should be a greater than zero");
 			return;
 		}