diff --git a/crates/uv-build-backend/src/source_dist.rs b/crates/uv-build-backend/src/source_dist.rs
index eec039cc9..b19c8aa48 100644
--- a/crates/uv-build-backend/src/source_dist.rs
+++ b/crates/uv-build-backend/src/source_dist.rs
@@ -285,7 +285,6 @@ impl DirectoryWriter for TarGzWriter {
         // Reasonable default to avoid 0o000 permissions, the user's umask will be applied on
         // unpacking.
         header.set_mode(0o644);
-        header.set_cksum();
         self.tar
             .append_data(&mut header, path, Cursor::new(bytes))
             .map_err(|err| Error::TarWrite(self.path.clone(), err))?;
@@ -307,7 +306,6 @@ impl DirectoryWriter for TarGzWriter {
             header.set_mode(0o644);
         }
         header.set_size(metadata.len());
-        header.set_cksum();
         let reader = BufReader::new(File::open(file)?);
         self.tar
             .append_data(&mut header, path, reader)
@@ -320,13 +318,9 @@ impl DirectoryWriter for TarGzWriter {
         // Directories are always executable, which means they can be listed.
         header.set_mode(0o755);
         header.set_entry_type(EntryType::Directory);
-        header
-            .set_path(directory)
-            .map_err(|err| Error::TarWrite(self.path.clone(), err))?;
         header.set_size(0);
-        header.set_cksum();
         self.tar
-            .append(&header, io::empty())
+            .append_data(&mut header, directory, io::empty())
             .map_err(|err| Error::TarWrite(self.path.clone(), err))?;
         Ok(())
     }
diff --git a/crates/uv/tests/it/build_backend.rs b/crates/uv/tests/it/build_backend.rs
index cebdbed01..422c0ea3f 100644
--- a/crates/uv/tests/it/build_backend.rs
+++ b/crates/uv/tests/it/build_backend.rs
@@ -547,3 +547,47 @@ fn build_module_name_normalization() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn build_sdist_with_long_path() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let temp_dir = TempDir::new()?;
+
+    context
+        .temp_dir
+        .child("pyproject.toml")
+        .write_str(indoc! {r#"
+        [project]
+        name = "foo"
+        version = "1.0.0"
+
+        [build-system]
+        requires = ["uv_build>=0.6,<0.7"]
+        build-backend = "uv_build"
+    "#})?;
+    context
+        .temp_dir
+        .child("src/foo/__init__.py")
+        .write_str(r#"print("Hi from foo")"#)?;
+
+    let long_path = format!("src/foo/l{}ng/__init__.py", "o".repeat(100));
+    context
+        .temp_dir
+        .child(long_path)
+        .write_str(r#"print("Hi from foo")"#)?;
+
+    uv_snapshot!(context
+        .build_backend()
+        .arg("build-sdist")
+        .arg(temp_dir.path())
+        .env("UV_PREVIEW", "1"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    foo-1.0.0.tar.gz
+
+    ----- stderr -----
+    "###);
+
+    Ok(())
+}