diff --git a/crates/uv-python/src/downloads.rs b/crates/uv-python/src/downloads.rs
index 51f6f1d45..2b0a7e669 100644
--- a/crates/uv-python/src/downloads.rs
+++ b/crates/uv-python/src/downloads.rs
@@ -772,7 +772,9 @@ impl ManagedPythonDownload {
 
         let temp_dir = tempfile::tempdir_in(scratch_dir).map_err(Error::DownloadDirError)?;
 
-        if let Some(python_builds_dir) = env::var_os(EnvVars::UV_PYTHON_CACHE_DIR) {
+        if let Some(python_builds_dir) =
+            env::var_os(EnvVars::UV_PYTHON_CACHE_DIR).filter(|s| !s.is_empty())
+        {
             let python_builds_dir = PathBuf::from(python_builds_dir);
             fs_err::create_dir_all(&python_builds_dir)?;
             let hash_prefix = match self.sha256 {