diff --git a/include/libvirt/virterror.h b/include/libvirt/virterror.h
index efa4796d9b..9cac437287 100644
--- a/include/libvirt/virterror.h
+++ b/include/libvirt/virterror.h
@@ -4,7 +4,7 @@
  * Description: Provides the interfaces of the libvirt library to handle
  *              errors raised while using the library.
  *
- * Copy:  Copyright (C) 2006, 2010 Red Hat, Inc.
+ * Copy:  Copyright (C) 2006, 2010-2011 Red Hat, Inc.
  *
  * See COPYING.LIB for the License of this software
  *
@@ -232,6 +232,8 @@ typedef enum {
     VIR_ERR_INVALID_DOMAIN_SNAPSHOT = 71,/* invalid domain snapshot */
     VIR_ERR_NO_DOMAIN_SNAPSHOT = 72,	/* domain snapshot not found */
     VIR_ERR_INVALID_STREAM = 73,        /* stream pointer not valid */
+    VIR_ERR_ARGUMENT_UNSUPPORTED = 74,  /* valid API use but unsupported by
+                                           the given driver */
 } virErrorNumber;
 
 /**
diff --git a/src/util/virterror.c b/src/util/virterror.c
index 07f8b45c47..9a27feb8fd 100644
--- a/src/util/virterror.c
+++ b/src/util/virterror.c
@@ -1183,6 +1183,12 @@ virErrorMsg(virErrorNumber error, const char *info)
             else
                 errmsg = _("invalid stream pointer in %s");
             break;
+        case VIR_ERR_ARGUMENT_UNSUPPORTED:
+            if (info == NULL)
+                errmsg = _("argument unsupported");
+            else
+                errmsg = _("argument unsupported: %s");
+            break;
     }
     return (errmsg);
 }