diff --git a/lib/rexml/parsers/baseparser.rb b/lib/rexml/parsers/baseparser.rb
index c83e7958..2f068e0c 100644
--- a/lib/rexml/parsers/baseparser.rb
+++ b/lib/rexml/parsers/baseparser.rb
@@ -138,6 +138,7 @@ module Private
       def initialize( source )
         self.stream = source
         @listeners = []
+        @prefixes = Set.new
       end
 
       def add_listener( listener )
@@ -253,7 +254,7 @@ def pull_event
                 @source.position = start_position
                 raise REXML::ParseException.new(message, @source)
               end
-              @nsstack.unshift(curr_ns=Set.new)
+              @nsstack.unshift(Set.new)
               name = parse_name(base_error_message)
               if @source.match(/\s*\[/um, true)
                 id = [nil, nil, nil]
@@ -437,12 +438,12 @@ def pull_event
               end
               tag = md[1]
               @document_status = :in_element
-              prefixes = Set.new
-              prefixes << md[2] if md[2]
+              @prefixes.clear
+              @prefixes << md[2] if md[2]
               @nsstack.unshift(curr_ns=Set.new)
-              attributes, closed = parse_attributes(prefixes, curr_ns)
+              attributes, closed = parse_attributes(@prefixes, curr_ns)
               # Verify that all of the prefixes have been defined
-              for prefix in prefixes
+              for prefix in @prefixes
                 unless @nsstack.find{|k| k.member?(prefix)}
                   raise UndefinedNamespaceException.new(prefix,@source,self)
                 end