diff --git a/PTMCMCSampler/PTMCMCSampler.py b/PTMCMCSampler/PTMCMCSampler.py
index 24283bc..4aa1fee 100755
--- a/PTMCMCSampler/PTMCMCSampler.py
+++ b/PTMCMCSampler/PTMCMCSampler.py
@@ -575,7 +575,7 @@ def PTMCMCOneStep(self, p0, lnlike0, lnprob0, iter):
                 self.jumpDict[jump_name][1] += 1
         # temperature swap
         if iter % self.Tskip == 0 and self.nchain > 1:
-            p0, lnlike0, lnprob0 = self.PTswap(p0, lnlike0)
+            p0, lnlike0, lnprob0 = self.PTswap(p0, lnlike0, lnprob0, iter)
 
         self.updateChains(p0, lnlike0, lnprob0, iter)