diff --git a/crates/engine/src/doc_path/tests.rs b/crates/engine/src/doc_path/tests.rs
index b8dcbc190..718af0e6f 100644
--- a/crates/engine/src/doc_path/tests.rs
+++ b/crates/engine/src/doc_path/tests.rs
@@ -35,9 +35,12 @@ impl Services for Recording {
 }
 
 /// Probes every file as a still.
+#[cfg(unix)]
 struct Stills;
 
+#[cfg(unix)]
 impl crate::Importer for Stills {
+    /// Treat an existing test file as a still image without decoding its bytes.
     fn probe(&self, path: &str) -> Result<Footage, String> {
         if !std::path::Path::new(path).is_file() {
             return Err(format!("{path}: no such file"));