Index: issue.rb
===================================================================
--- issue.rb	(revision 1674)
+++ issue.rb	(working copy)
@@ -74,7 +74,9 @@
           self.relations_to.clear
         end
         # issue is moved to another project
-        self.category = nil 
+        ic = IssueCategory.find(:first, :conditions=>["project_id=? and name=?",
+          new_project.id, self.category.name]) if self.category
+        ic ? self.category = ic : self.category = nil
         self.fixed_version = nil
         self.project = new_project
       end