diff --git a/src/integrated.rs b/src/integrated.rs
index c2dd810..341c448 100644
--- a/src/integrated.rs
+++ b/src/integrated.rs
@@ -99,7 +99,11 @@ pub fn generate_flatmap(xml: &path::Path, out: Option<&path::Path>) -> Result<()
     }
     let f: Box<dyn Write> = match out {
         Some(f) => {
-            let file = File::options().write(true).truncate(true).open(f)?;
+            let file = File::options()
+                .create(true)
+                .write(true)
+                .truncate(true)
+                .open(f)?;
             Box::new(BufWriter::new(file))
         }
         None => Box::new(io::stdout()),