diff --git a/lib/constants.py b/lib/constants.py
index 4e388b8bc857335ccb8ee593b1c70c4c31174efd..32aa2acf71bf3b1f4c25e22b343e6823191ea99e 100644
--- a/lib/constants.py
+++ b/lib/constants.py
@@ -441,6 +441,7 @@ IP6_ADDRESS_ANY = "::"
 TCP_PING_TIMEOUT = 10
 GANETI_RUNAS = "root"
 DEFAULT_VG = "xenvg"
+DEFAULT_DRBD_HELPER = "/bin/true"
 MIN_VG_SIZE = 20480
 DEFAULT_MAC_PREFIX = "aa:00:00"
 LVM_STRIPECOUNT = _autoconf.LVM_STRIPECOUNT
diff --git a/lib/objects.py b/lib/objects.py
index 9e9163cbbade3db9907f7623ca5f201cb63ae240..42036e180ad2847050386e34868aa98cd7815efc 100644
--- a/lib/objects.py
+++ b/lib/objects.py
@@ -364,6 +364,12 @@ class ConfigData(ConfigObject):
       node.UpgradeConfig()
     for instance in self.instances.values():
       instance.UpgradeConfig()
+    if self.cluster.drbd_usermode_helper is None:
+      # To decide if we set an helper let's check if at least one instance has
+      # a DRBD disk. This does not cover all the possible scenarios but it
+      # gives a good approximation.
+      if self.HasAnyDiskOfType(constants.LD_DRBD8):
+        self.cluster.drbd_usermode_helper = constants.DEFAULT_DRBD_HELPER
 
 
 class NIC(ConfigObject):