diff --git a/pkgs/build-support/fetchfossil/nix-prefetch-fossil b/pkgs/build-support/fetchfossil/nix-prefetch-fossil
index 1f3c2636355e..0e1ce4d9c060 100755
--- a/pkgs/build-support/fetchfossil/nix-prefetch-fossil
+++ b/pkgs/build-support/fetchfossil/nix-prefetch-fossil
@@ -89,10 +89,15 @@ fossil open "$tmpPath/fossil-clone.fossil" "$rev" >&2
 
 # Get the actual commit hash and date
 checkoutLine=$(fossil info | grep ^checkout:)
-# Remove 'checkout:' prefix and squeeze multiple spaces, then extract fields
-actualRev=$(echo "$checkoutLine" | sed 's/^checkout:[[:space:]]*//' | tr -s ' ' | cut -d' ' -f1)
-# Extract date (format: checkout:     HASH YYYY-MM-DD HH:MM:SS UTC)
-actualDate=$(echo "$checkoutLine" | sed 's/^checkout:[[:space:]]*//' | tr -s ' ' | cut -d' ' -f2)
+# Remove 'checkout:' prefix & remove whitespace
+checkoutData=$(echo "$checkoutLine" | sed 's/^checkout:[[:space:]]*//' | tr -s ' ')
+# Extract fields: HASH YYYY-MM-DD HH:MM:SS UTC
+actualRev=$(echo "$checkoutData" | cut -d' ' -f1)
+# Get datetime parts
+rawDate=$(echo "$checkoutData" | cut -d' ' -f2)
+rawTime=$(echo "$checkoutData" | cut -d' ' -f3)
+# Combine into ISO 8601 RFC 3339 format
+actualDatetime="${rawDate}T${rawTime}Z"
 cd - >/dev/null
 
 # Remove the fossil checkout file
@@ -118,7 +123,8 @@ cat <<EOF
 {
   "url": "$url",
   "rev": "$actualRev",
-  "date": "$actualDate",
+  "date": "$actualDatetime",
+  "path": "$finalPath",
   "$hashType": "$hash",
   "hash": "$(nix-hash --to-sri --type $hashType $hash)"
 }
diff --git a/pkgs/tools/package-management/nix-prefetch-scripts/default.nix b/pkgs/tools/package-management/nix-prefetch-scripts/default.nix
index 015c46bc6d9f..123ea0d71b94 100644
--- a/pkgs/tools/package-management/nix-prefetch-scripts/default.nix
+++ b/pkgs/tools/package-management/nix-prefetch-scripts/default.nix
@@ -71,6 +71,8 @@ rec {
     mkPrefetchScript "fossil" ../../../build-support/fetchfossil/nix-prefetch-fossil
       [
         fossil
+        gnugrep
+        gnused
       ];
   nix-prefetch-git = mkPrefetchScript "git" ../../../build-support/fetchgit/nix-prefetch-git [
     findutils
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index facde1759ec5..4a786b2e13f0 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -12607,6 +12607,7 @@ with pkgs;
     nix-prefetch-bzr
     nix-prefetch-cvs
     nix-prefetch-darcs
+    nix-prefetch-fossil
     nix-prefetch-git
     nix-prefetch-hg
     nix-prefetch-pijul