diff --git a/crates/usvg/src/tree/mod.rs b/crates/usvg/src/tree/mod.rs
index f2f9b6e34..70916da30 100644
--- a/crates/usvg/src/tree/mod.rs
+++ b/crates/usvg/src/tree/mod.rs
@@ -73,6 +73,15 @@ pub(crate) enum Units {
 
 // `Units` cannot have a default value, because it changes depending on an element.
 
+impl std::fmt::Display for Units {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Units::UserSpaceOnUse => write!(f, "userSpaceOnUse"),
+            Units::ObjectBoundingBox => write!(f, "objectBoundingBox"),
+        }
+    }
+}
+
 /// A visibility property.
 ///
 /// `visibility` attribute in the SVG.
diff --git a/crates/usvg/src/writer.rs b/crates/usvg/src/writer.rs
index 96444043d..231f84467 100644
--- a/crates/usvg/src/writer.rs
+++ b/crates/usvg/src/writer.rs
@@ -987,16 +987,9 @@ impl XmlWriterExt for XmlWriter {
         });
     }
 
-    // TODO: simplify
     fn write_units(&mut self, id: AId, units: Units, def: Units) {
         if units != def {
-            self.write_attribute(
-                id.to_str(),
-                match units {
-                    Units::UserSpaceOnUse => "userSpaceOnUse",
-                    Units::ObjectBoundingBox => "objectBoundingBox",
-                },
-            );
+            self.write_attribute(id.to_str(), &units);
         }
     }