diff --git a/src/main/java/hudson/plugins/ec2/util/MinimumInstanceChecker.java b/src/main/java/hudson/plugins/ec2/util/MinimumInstanceChecker.java
index bca67225f..fadd0094d 100644
--- a/src/main/java/hudson/plugins/ec2/util/MinimumInstanceChecker.java
+++ b/src/main/java/hudson/plugins/ec2/util/MinimumInstanceChecker.java
@@ -41,7 +41,7 @@ public static int countCurrentNumberOfAgents(@Nonnull SlaveTemplate agentTemplat
 
     public static int countCurrentNumberOfSpareAgents(@Nonnull SlaveTemplate agentTemplate) {
         return (int) agentsForTemplate(agentTemplate)
-            .filter(computer -> computer.countBusy() == 0)
+            .filter(computer -> computer.countIdle() > 0)
             .filter(computer -> computer.isOnline())
             .count();
     }