diff --git a/lib/odba/cache.rb b/lib/odba/cache.rb
index 7116467..07f41bd 100644
--- a/lib/odba/cache.rb
+++ b/lib/odba/cache.rb
@@ -68,29 +68,31 @@ module ODBA
 			retrieved_objects
 		end
 		def clean # :nodoc:
-      now = Time.now
-      start = Time.now if(@debug)
-			@cleaned = 0
-      if(@debug)
-        puts "starting cleaning cycle"
-        $stdout.flush
-      end
-      retire_horizon = now - @retire_age
-      @cleaner_offset = _clean(retire_horizon, @fetched, @cleaner_offset)
-			if(@clean_prefetched)
-        @prefetched_offset = _clean(retire_horizon, @prefetched, 
-                                    @prefetched_offset)
-			end
-      if(@debug)
-        puts "cleaned: #{@cleaned} objects in #{Time.now - start} seconds"
-        puts "remaining objects in @fetched:    #{@fetched.size}"
-        puts "remaining objects in @prefetched: #{@prefetched.size}"
-        mbytes = File.read("/proc/#{$$}/stat").split(' ').at(22).to_i / (2**20)
-        GC.start
-        puts "remaining objects in ObjectSpace: #{ObjectSpace.each_object {}}"
-        puts "memory-usage:                     #{mbytes}MB"
-        $stdout.flush
-      end
+      @cache_mutex.synchronize {
+        now = Time.now
+        start = Time.now if(@debug)
+        @cleaned = 0
+        if(@debug)
+          puts "starting cleaning cycle"
+          $stdout.flush
+        end
+        retire_horizon = now - @retire_age
+        @cleaner_offset = _clean(retire_horizon, @fetched, @cleaner_offset)
+        if(@clean_prefetched)
+          @prefetched_offset = _clean(retire_horizon, @prefetched, 
+                                      @prefetched_offset)
+        end
+        if(@debug)
+          puts "cleaned: #{@cleaned} objects in #{Time.now - start} seconds"
+          puts "remaining objects in @fetched:    #{@fetched.size}"
+          puts "remaining objects in @prefetched: #{@prefetched.size}"
+          mbytes = File.read("/proc/#{$$}/stat").split(' ').at(22).to_i / (2**20)
+          GC.start
+          puts "remaining objects in ObjectSpace: #{ObjectSpace.each_object {}}"
+          puts "memory-usage:                     #{mbytes}MB"
+          $stdout.flush
+        end
+      }
 		end
     def _clean(retire_time, holder, offset) # :nodoc: 
       if(offset > holder.size) 
@@ -98,14 +100,12 @@ module ODBA
       end
       counter = 0
       cutoff = offset + @cleaner_step
-      @cache_mutex.synchronize {
-        holder.each_value { |value|
-          counter += 1
-          if(counter > offset && value.odba_old?(retire_time))
-            value.odba_retire && @cleaned += 1
-          end
-          return cutoff if(counter > cutoff)
-        }
+      holder.each_value { |value|
+        counter += 1
+        if(counter > offset && value.odba_old?(retire_time))
+          value.odba_retire && @cleaned += 1
+        end
+        return cutoff if(counter > cutoff)
       }
       cutoff 
     # every once in a while we'll get a 'hash modified during iteration'-Error.