If its not a markdown file just return the file name itself, because then it's probably a directory.

src/lib.rs

@@ -321,7 +321,12 @@ fn render_markdown (content: &tera::Value, args: &HashMap<String, tera::Value>)
 }
 
 fn file_stem (content: &tera::Value, args: &HashMap<String, tera::Value>) -> tera::Result<tera::Value> {
-    Ok(tera::Value::String(Path::new(content.as_str().expect("as_str")).file_stem().expect("file_stem").to_str().expect("to_str").to_owned()))
+    let content_as_str = content.as_str().expect("as_str");
+    if !content_as_str.ends_with(MD_EXTENSION) {
+        Ok(content.clone())
+    } else {      
+        Ok(tera::Value::String(Path::new(content_as_str).file_stem().expect("file_stem").to_str().expect("to_str").to_owned()))
+    }
 }
 
 impl PageRenderer {