diff --git a/crates/engine/src/cmd/layout.rs b/crates/engine/src/cmd/layout.rs
index 5a0a4000..22f50b0f 100644
--- a/crates/engine/src/cmd/layout.rs
+++ b/crates/engine/src/cmd/layout.rs
@@ -181,6 +181,19 @@ mod tests {
         assert!(s.execute("node.set", &json!({"id": f, "props": {"paddingLeft": "wide"}})).is_err());
     }
 
+    #[test]
+    fn junk_axis_padding_is_refused_and_keeps_padding() {
+        let mut s = Session::new();
+        let (f, _, _) = al_frame(&mut s);
+        ex(&mut s, "node.set", json!({"id": f, "props": {"padding": 16}}));
+        for key in ["paddingHorizontal", "paddingVertical"] {
+            for junk in [json!("abc"), json!({"a": 1}), json!([1, 2])] {
+                assert!(s.execute("node.set", &json!({"id": f, "props": {key: junk}})).is_err(), "{key}");
+                assert_eq!(node(&s, f).layout.as_ref().unwrap().padding, [16.0; 4], "{key}");
+            }
+        }
+    }
+
     #[test]
     fn baseline_alignment_lines_up_text() {
         let mut s = Session::new();
diff --git a/crates/engine/src/cmd/props.rs b/crates/engine/src/cmd/props.rs
index 30a10393..8c09a9b6 100644
--- a/crates/engine/src/cmd/props.rs
+++ b/crates/engine/src/cmd/props.rs
@@ -621,13 +621,13 @@ pub fn apply(cmd: &str, doc: &mut Document, id: NodeId, props: &Map<String, Valu
                 }
             }
             "paddingHorizontal" => {
-                let val = f64_of(v).unwrap_or(0.0).max(0.0);
+                let val = f64_of(v).ok_or_else(|| bad(cmd, format!("`{k}` must be a number")))?.max(0.0);
                 let l = layout_mut(cmd, k, doc.get_mut(id)?)?;
                 l.padding[1] = val;
                 l.padding[3] = val;
             }
             "paddingVertical" => {
-                let val = f64_of(v).unwrap_or(0.0).max(0.0);
+                let val = f64_of(v).ok_or_else(|| bad(cmd, format!("`{k}` must be a number")))?.max(0.0);
                 let l = layout_mut(cmd, k, doc.get_mut(id)?)?;
                 l.padding[0] = val;
                 l.padding[2] = val;