Hi David, That was indeed the correct fix. Thanks for pointing out the error, the fix will be included in the next release. Jeremy > I did remove "queue" and that compiled - > > "if (EnsureSize(GetNumItems()+numItems) !=3D B=5FNO=5FERROR) return > B=5FERROR;" at > line 511 in MUSCLE 2.43. > > /D