diff --git a/_doc/dejure/CHANGELOG b/_doc/dejure/CHANGELOG
index d4b30cf..039edf3 100644
--- a/_doc/dejure/CHANGELOG
+++ b/_doc/dejure/CHANGELOG
@@ -4,6 +4,7 @@
 
 ### Version 0.3 (unreleased)
 
+* Save space by caching just '<!-- idem -->' for unchanged texts.
 * Change protocol to https.
 * Make cache validity configurable.
 * Rename from "DejureIntegrator" to "DejureAutolinker".
diff --git a/lib/filters/dejure.rb b/lib/filters/dejure.rb
index fd251d4..ac40e72 100644
--- a/lib/filters/dejure.rb
+++ b/lib/filters/dejure.rb
@@ -124,7 +124,13 @@ module Nanoc::Filters
       cache_file = cache_dir + '/' + cache_filename(input)
       if File.directory?(cache_dir)
         File.open(cache_file, 'w') do |f|
-          f.write(output)
+          # if input is unchanged, just save '<!-- idem -->'
+          # instead of the whole (unchanged) text to save space
+          if input == output
+            f.write('<!-- idem -->')
+          else
+            f.write(output)
+          end
         end
       end
     end
@@ -133,7 +139,13 @@ module Nanoc::Filters
       cache_file = cache_dir + '/' + cache_filename(input)
       # file exists and is younger than cache_days?
       if File.exist?(cache_file) && File.mtime(cache_file).to_i > cache_age(cache_days)
-        return File.read(cache_file)
+        output = File.read(cache_file)
+        # if just '<!-- idem -->' is cached, return input unchanged
+        if output == '<!-- idem -->'
+          return input
+        else
+          return output
+        end
       else
         return false
       end