diff --git a/lib/puppet/parser/relationship.rb b/lib/puppet/parser/relationship.rb
index c88a7a2fb..92ba4071a 100644
--- a/lib/puppet/parser/relationship.rb
+++ b/lib/puppet/parser/relationship.rb
@@ -1,44 +1,60 @@
 class Puppet::Parser::Relationship
   attr_accessor :source, :target, :type
 
   PARAM_MAP = {:relationship => :before, :subscription => :notify}
 
   def arrayify(resources)
     case resources
     when Puppet::Parser::Collector
       resources.collected.values
     when Array
       resources
     else
       [resources]
     end
   end
 
   def evaluate(catalog)
     arrayify(source).each do |s|
       arrayify(target).each do |t|
         mk_relationship(s, t, catalog)
       end
     end
   end
 
   def initialize(source, target, type)
     @source, @target, @type = source, target, type
   end
 
   def param_name
     PARAM_MAP[type] || raise(ArgumentError, "Invalid relationship type #{type}")
   end
 
   def mk_relationship(source, target, catalog)
-    unless source_resource = catalog.resource(source.to_s)
+    # REVISIT: In Ruby 1.8 we applied `to_s` to source and target, rather than
+    # `join` without an argument.  In 1.9 the behaviour of Array#to_s changed,
+    # and it gives a different representation than just concat the stringified
+    # elements.
+    #
+    # This restores the behaviour, but doesn't address the underlying question
+    # of what would happen when more than one item was passed in that array.
+    # (Hint: this will not end well.)
+    #
+    # See http://projects.puppetlabs.com/issues/12076 for the ticket tracking
+    # the fact that we should dig out the sane version of this behaviour, then
+    # implement it - where we don't risk breaking a stable release series.
+    # --daniel 2012-01-21
+    source = source.is_a?(Array) ? source.join : source.to_s
+    target = target.is_a?(Array) ? target.join : target.to_s
+
+    unless source_resource = catalog.resource(source)
       raise ArgumentError, "Could not find resource '#{source}' for relationship on '#{target}'"
     end
-    unless target_resource = catalog.resource(target.to_s)
+    unless target_resource = catalog.resource(target)
       raise ArgumentError, "Could not find resource '#{target}' for relationship from '#{source}'"
     end
-    Puppet.debug "Adding relationship from #{source.to_s} to #{target.to_s} with '#{param_name}'"
+    Puppet.debug "Adding relationship from #{source} to #{target} with '#{param_name}'"
     source_resource[param_name] ||= []
-    source_resource[param_name] << target.to_s
+    source_resource[param_name] << target
   end
 end