diff --git a/app/models/relation.rb b/app/models/relation.rb
index 3d3c317aa..cb9621822 100644
--- a/app/models/relation.rb
+++ b/app/models/relation.rb
@@ -246,8 +246,10 @@ class Relation < ActiveRecord::Base
 
       # use reflection to look up the appropriate class
       model = Kernel.const_get(m[0].capitalize)
-      # get the element with that ID
-      element = model.find_by(:id => m[1])
+      # get the element with that ID. and, if found, lock the element to
+      # ensure it can't be deleted until after the current transaction
+      # commits.
+      element = model.lock("for share").find_by(:id => m[1])
 
       # and check that it is OK to use.
       unless element && element.visible? && element.preconditions_ok?
diff --git a/app/models/way.rb b/app/models/way.rb
index 34e568e4a..6d49735f1 100644
--- a/app/models/way.rb
+++ b/app/models/way.rb
@@ -199,7 +199,9 @@ class Way < ActiveRecord::Base
     new_nds = (nds - old_nodes).sort.uniq
 
     unless new_nds.empty?
-      db_nds = Node.where(:id => new_nds, :visible => true)
+      # NOTE: nodes are locked here to ensure they can't be deleted before
+      # the current transaction commits.
+      db_nds = Node.where(:id => new_nds, :visible => true).lock("for share")
 
       if db_nds.length < new_nds.length
         missing = new_nds - db_nds.collect(&:id)