diff --git a/ngcp/pp.lua b/ngcp/pp.lua
index a452f28..e1c9bcc 100644
--- a/ngcp/pp.lua
+++ b/ngcp/pp.lua
@@ -19,6 +19,7 @@
 --
 local utils = require 'ngcp.utils'
 local NGCPPrefs = require 'ngcp.pref'
+local NGCPXAvp = require 'ngcp.xavp'
 
 -- class NGCPPeerPrefs
 local NGCPPeerPrefs = utils.inheritsFrom(NGCPPrefs)
@@ -35,5 +36,15 @@ function NGCPPeerPrefs:new(config)
     return instance
 end
 
+function NGCPPeerPrefs:clean(vtype)
+    NGCPPrefs.clean(self, vtype)
+    if not vtype then
+        NGCPXAvp:new('callee', 'prefs'):clean()
+        NGCPXAvp:new('caller', 'prefs'):clean()
+    else
+        NGCPXAvp:new(vtype, 'prefs'):clean()
+    end
+end
+
 -- class
 return NGCPPeerPrefs
diff --git a/tests/ngcp_pp.lua b/tests/ngcp_pp.lua
index af494da..5f7793d 100644
--- a/tests/ngcp_pp.lua
+++ b/tests/ngcp_pp.lua
@@ -22,7 +22,7 @@ local lemock = require('lemock')
 local utils = require 'ngcp.utils'
 local utable = utils.table
 local PPFetch = require 'tests_v.pp_vars'
-
+local NGCPXAvp = require 'ngcp.xavp'
 
 local ksrMock = require 'mocks.ksr'
 KSR = ksrMock:new()
@@ -234,6 +234,24 @@ TestNGCPPeerPrefs = {} --class
         lu.assertEquals(KSR.pv.get("$xavp(callee_peer_prefs=>dummy)"),"callee")
     end
 
+    function TestNGCPPeerPrefs:test_clean_prefs()
+        local xavp_pref = NGCPXAvp:new('callee', 'prefs')
+        local xavp = NGCPPeerPrefs:xavp('callee')
+        xavp("testid",1)
+        xavp("foo","foo")
+        xavp_pref("two",2)
+        lu.assertEquals(KSR.pv.get("$xavp(callee_prefs=>two)"),2)
+        lu.assertEquals(KSR.pv.get("$xavp(callee_peer_prefs=>testid)"),1)
+        lu.assertEquals(KSR.pv.get("$xavp(callee_peer_prefs=>foo)"),"foo")
+        lu.assertEquals(KSR.pv.get("$xavp(caller_peer_prefs=>dummy)"),"caller")
+        lu.assertEquals(KSR.pv.get("$xavp(callee_peer_prefs=>dummy)"),"callee")
+        self.d:clean('callee')
+        lu.assertEquals(KSR.pv.get("$xavp(caller_peer_prefs=>dummy)"),"caller")
+        lu.assertEquals(KSR.pv.get("$xavp(callee_peer_prefs=>dummy)"),"callee")
+        lu.assertNil(KSR.pv.get("$xavp(peer)"))
+        lu.assertEquals(KSR.pv.get("$xavp(callee_prefs=>dummy)"), "callee")
+    end
+
     function TestNGCPPeerPrefs:test_tostring()
         local callee_xavp = NGCPPeerPrefs:xavp('callee')
         callee_xavp("testid",1)