diff --git a/src/main/java/hudson/plugins/ec2/SlaveTemplate.java b/src/main/java/hudson/plugins/ec2/SlaveTemplate.java
index 5656c79b7..0b2cd4330 100644
--- a/src/main/java/hudson/plugins/ec2/SlaveTemplate.java
+++ b/src/main/java/hudson/plugins/ec2/SlaveTemplate.java
@@ -961,7 +961,11 @@ private void setupRootDevice(List<BlockDeviceMapping> deviceMappings) {
                 LOGGER.warning("AMI missing block devices");
                 return;
             }
-            BlockDeviceMapping rootMapping = rootDeviceMappings.get(0);
+            BlockDeviceMapping rootMapping = getRootDeviceMapping(rootDeviceMappings);
+            if (rootMapping==null) {
+                LOGGER.warning("AMI missing root device");
+                return;
+            }
             LOGGER.info("AMI had " + rootMapping.getDeviceName());
             LOGGER.info(rootMapping.getEbs().toString());
 
@@ -984,6 +988,12 @@ private void setupRootDevice(List<BlockDeviceMapping> deviceMappings) {
         }
     }
 
+    private BlockDeviceMapping getRootDeviceMapping(List<BlockDeviceMapping> deviceMappings) {
+        return deviceMappings.stream().filter(mapping -> mapping.getDeviceName().equals(getImage().getRootDeviceName()))
+                .findFirst()
+                .orElse(null);
+    }
+
     private List<BlockDeviceMapping> getNewEphemeralDeviceMapping() {
 
         final List<BlockDeviceMapping> oldDeviceMapping = getAmiBlockDeviceMappings();