diff --git a/pkgs/build-support/fetchfossil/default.nix b/pkgs/build-support/fetchfossil/default.nix
index 3f3bf69db047..d0fc4cdea703 100644
--- a/pkgs/build-support/fetchfossil/default.nix
+++ b/pkgs/build-support/fetchfossil/default.nix
@@ -1,33 +1,26 @@
 {stdenv, lib, fossil, cacert}:
 
-{ name ? null
-, url
-, rev
-, sha256 ? ""
-, hash ? ""
-}:
+lib.fetchers.withNormalizedHash { } (
+  { name ? null
+  , url
+  , rev
+  , outputHash ? lib.fakeHash
+  , outputHashAlgo ? null
+  }:
 
-if hash != "" && sha256 != "" then
-  throw "Only one of sha256 or hash can be set"
-else
-stdenv.mkDerivation {
-  name = "fossil-archive" + (lib.optionalString (name != null) "-${name}");
-  builder = ./builder.sh;
-  nativeBuildInputs = [fossil cacert];
+  stdenv.mkDerivation {
+    name = "fossil-archive" + (lib.optionalString (name != null) "-${name}");
+    builder = ./builder.sh;
+    nativeBuildInputs = [fossil cacert];
 
-  # Envvar docs are hard to find. A link for the future:
-  # https://www.fossil-scm.org/index.html/doc/trunk/www/env-opts.md
-  impureEnvVars = [ "http_proxy" ];
+    # Envvar docs are hard to find. A link for the future:
+    # https://www.fossil-scm.org/index.html/doc/trunk/www/env-opts.md
+    impureEnvVars = [ "http_proxy" ];
 
-  outputHashAlgo = if hash != "" then null else "sha256";
-  outputHashMode = "recursive";
-  outputHash = if hash != "" then
-    hash
-  else if sha256 != "" then
-    sha256
-  else
-    lib.fakeSha256;
+    inherit outputHash outputHashAlgo;
+    outputHashMode = "recursive";
 
-  inherit url rev;
-  preferLocalBuild = true;
-}
+    inherit url rev;
+    preferLocalBuild = true;
+  }
+)