diff --git a/src/libfetchers/tarball.cc b/src/libfetchers/tarball.cc
index c2bf23332..07ce05506 100644
--- a/src/libfetchers/tarball.cc
+++ b/src/libfetchers/tarball.cc
@@ -230,7 +230,7 @@ struct CurlInputScheme : InputScheme
         if (type != inputType()) return {};
 
         // FIXME: some of these only apply to TarballInputScheme.
-        std::set<std::string> allowedNames = {"type", "url", "narHash", "name", "unpack", "rev", "revCount"};
+        std::set<std::string> allowedNames = {"type", "url", "narHash", "name", "unpack", "rev", "revCount", "lastModified"};
         for (auto & [name, value] : attrs)
             if (!allowedNames.count(name))
                 throw Error("unsupported %s input attribute '%s'", *type, name);
@@ -308,6 +308,9 @@ struct TarballInputScheme : CurlInputScheme
             input = immutableInput;
         }
 
+        if (result.lastModified && !input.attrs.contains("lastModified"))
+            input.attrs.insert_or_assign("lastModified", uint64_t(result.lastModified));
+
         return {result.tree.storePath, std::move(input)};
     }
 };
diff --git a/tests/tarball.sh b/tests/tarball.sh
index d5cab879c..9ab212a95 100644
--- a/tests/tarball.sh
+++ b/tests/tarball.sh
@@ -9,6 +9,7 @@ rm -rf $tarroot
 mkdir -p $tarroot
 cp dependencies.nix $tarroot/default.nix
 cp config.nix dependencies.builder*.sh $tarroot/
+touch -d '@1000000000' $tarroot $tarroot/*
 
 hash=$(nix hash path $tarroot)
 
@@ -36,6 +37,8 @@ test_tarball() {
     nix-build  -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file:///does-not-exist/must-remain-unused/$tarball; narHash = \"$hash\"; })"
     nix-build  -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file://$tarball; narHash = \"sha256-xdKv2pq/IiwLSnBBJXW8hNowI4MrdZfW+SYqDQs7Tzc=\"; })" 2>&1 | grep 'NAR hash mismatch in input'
 
+    [[ $(nix eval --impure --expr "(fetchTree file://$tarball).lastModified") = 1000000000 ]]
+
     nix-instantiate --strict --eval -E "!((import (fetchTree { type = \"tarball\"; url = file://$tarball; narHash = \"$hash\"; })) ? submodules)" >&2
     nix-instantiate --strict --eval -E "!((import (fetchTree { type = \"tarball\"; url = file://$tarball; narHash = \"$hash\"; })) ? submodules)" 2>&1 | grep 'true'