diff --git a/flake.nix b/flake.nix
index 7723128..d52cf16 100644
--- a/flake.nix
+++ b/flake.nix
@@ -51,82 +51,117 @@
         platforms = lib.platforms.all;
       };
     in forAllSystems (system: pkgs: {
-      jmdict = pkgs.stdenvNoCC.mkDerivation {
+      jmdict = pkgs.stdenvNoCC.mkDerivation (finalAttrs: {
         pname = "jmdict";
         version = lib.fileContents ./jmdict/version.txt;
+        src = ./jmdict/jmdict.xml;
 
         dontUnpack = true;
         dontBuild = true;
         installPhase = ''
           runHook preInstall
 
-          install -Dm644 '${./jmdict/jmdict.xml}' "$out/JMdict.xml"
+          install -Dm644 "$src" "$out/JMdict.xml"
 
           runHook postInstall
         '';
 
+        passthru = {
+          hash = lib.hashFile "sha256" finalAttrs.src;
+          date = lib.fileContents ./jmdict/version.txt;
+        };
+
         meta = edrdgMetadata // {
           description = "A Japanese-Multilingual Dictionary providing lexical data for japanese words";
           homepage = "https://www.edrdg.org/jmdict/j_jmdict.html";
         };
-      };
+      });
 
-      kanjidic2 = pkgs.stdenvNoCC.mkDerivation {
+      kanjidic2 = pkgs.stdenvNoCC.mkDerivation (finalAttrs: {
         pname = "kanjidic2";
         version = lib.fileContents ./kanjidic2/version.txt;
+        src = ./kanjidic2/kanjidic2.xml;
 
         dontUnpack = true;
         dontBuild = true;
         installPhase = ''
           runHook preInstall
 
-          install -Dm644 '${./kanjidic2/kanjidic2.xml}' "$out/kanjidic2.xml"
+          install -Dm644 "$src" "$out/kanjidic2.xml"
 
           runHook postInstall
         '';
 
+        passthru = {
+          hash = lib.hashFile "sha256" finalAttrs.src;
+          date = lib.pipe ./kanjidic2/version.txt [
+            lib.fileContents
+            (lib.splitString ".")
+            lib.head
+          ];
+        };
+
         meta = edrdgMetadata // {
           description = "A consolidated XML-format kanji database";
           homepage = "https://www.edrdg.org/kanjidic/kanjd2index_legacy.html";
         };
-      };
+      });
 
-      radkfile = pkgs.stdenvNoCC.mkDerivation {
+      radkfile = pkgs.stdenvNoCC.mkDerivation (finalAttrs: {
         pname = "radkfile";
         version = lib.fileContents ./radkfile/version.txt;
+        src = ./radkfile/radkfile;
 
         dontUnpack = true;
         dontBuild = true;
         installPhase = ''
           runHook preInstall
 
-          install -Dm644 ${./radkfile/radkfile} "$out/RADKFILE"
+          install -Dm644 "$src" "$out/RADKFILE"
 
           runHook postInstall
         '';
 
+        passthru = {
+          hash = lib.hashFile "sha256" finalAttrs.src;
+          date = lib.fileContents ./radkfile/version.txt;
+        };
+
         meta = edrdgMetadata // {
           description = "A file providing searchable decompositions of kanji characters";
           homepage = "https://www.edrdg.org/krad/kradinf.html";
         };
-      };
+      });
 
-      tanos-jlpt = pkgs.stdenvNoCC.mkDerivation {
+      tanos-jlpt = pkgs.stdenvNoCC.mkDerivation (finalAttrs: {
         pname = "tanos-jlpt";
         version = "2011";
+        src = ./tanos-jlpt;
 
         dontUnpack = true;
         dontBuild = true;
         installPhase = ''
           runHook preInstall
 
-          for f in ${./tanos-jlpt}/*.csv; do
+          for f in "$src"/*.csv; do
             install -Dm644 -t "$out" "$f"
           done
 
           runHook postInstall
         '';
 
+        passthru = {
+          hash = lib.pipe finalAttrs.src [
+            lib.readDir
+            lib.attrNames
+            (lib.filter (lib.hasSuffix ".csv"))
+            (map (filename: lib.hashFile "sha256" /${finalAttrs.src}/${filename}))
+            (lib.concatStringsSep "")
+            (lib.hashString "sha256")
+          ];
+          date = "2011";
+        };
+
         meta = {
           description = "A CSV file containing JLPT-rated Japanese vocabulary";
           homepage = "https://www.tanos.co.uk/jlpt/";
@@ -134,7 +169,7 @@
           maintainers = [ lib.maintainers.h7x4 ];
           platforms = lib.platforms.all;
         };
-      };
+      });
     });
   };
 }