diff --git a/crates/slideshow/src/settings.rs b/crates/slideshow/src/settings.rs
index fd3b327ef..488819e77 100644
--- a/crates/slideshow/src/settings.rs
+++ b/crates/slideshow/src/settings.rs
@@ -218,22 +218,35 @@ impl SlideSettings {
 
     /// These settings with the keys `p` names changed (the others kept), validated and clamped.
     /// A wrong type, an unknown key or a non-finite number is an error, and nothing changes.
-    /// With `linkMargins` on (already, or set in `p`), a margin given sets all four; `margins`
-    /// sets all four in any case.
+    /// With `linkMargins` on (already, or set in `p`), a margin given sets all four (unless all four are given);
+    /// `margins` sets all four in any case.
     pub fn merged(&self, p: &Value) -> Result<Self, String> {
         let Some(obj) = p.as_object() else { return Err("parameters must be an object".into()) };
         let mut s = self.clone();
         let mut margin: Option<f64> = None;
+        let mut margin_keys = 0;
         for (k, v) in obj {
             match k.as_str() {
                 "margins" => {
                     let m = number(k, v)?;
                     (s.margin_left, s.margin_right, s.margin_top, s.margin_bottom) = (m, m, m, m);
                 }
-                "marginLeft" => s.margin_left = *margin.insert(number(k, v)?),
-                "marginRight" => s.margin_right = *margin.insert(number(k, v)?),
-                "marginTop" => s.margin_top = *margin.insert(number(k, v)?),
-                "marginBottom" => s.margin_bottom = *margin.insert(number(k, v)?),
+                "marginLeft" => {
+                    s.margin_left = *margin.insert(number(k, v)?);
+                    margin_keys += 1;
+                }
+                "marginRight" => {
+                    s.margin_right = *margin.insert(number(k, v)?);
+                    margin_keys += 1;
+                }
+                "marginTop" => {
+                    s.margin_top = *margin.insert(number(k, v)?);
+                    margin_keys += 1;
+                }
+                "marginBottom" => {
+                    s.margin_bottom = *margin.insert(number(k, v)?);
+                    margin_keys += 1;
+                }
                 "linkMargins" => s.link_margins = boolean(k, v)?,
                 "showGuides" => s.show_guides = boolean(k, v)?,
                 "aspect" => {
@@ -264,7 +277,9 @@ impl SlideSettings {
                 other => return Err(format!("unknown setting `{other}` ({KEYS})")),
             }
         }
+        // all four given: an explicit full state (e.g. `to_json`), kept as is
         if s.link_margins
+            && margin_keys < 4
             && let Some(m) = margin
         {
             (s.margin_left, s.margin_right, s.margin_top, s.margin_bottom) = (m, m, m, m);
@@ -319,6 +334,21 @@ pub fn hex(c: [u8; 3]) -> String {
 mod tests {
     use super::*;
 
+    #[test]
+    fn merge_restores_unequal_linked_margins() {
+        let d = SlideSettings::default();
+        let st = SlideSettings { link_margins: true, margin_left: 0.1, margin_right: 0.0, margin_top: 0.3, margin_bottom: 0.0, ..d.clone() };
+        assert_eq!(d.merged(&st.to_json()).unwrap(), st);
+    }
+
+    #[test]
+    fn merge_copies_last_of_three_linked_margins() {
+        let d = SlideSettings::default();
+        // keys are visited in key order (bottom, left, top): the last one, `marginTop`, wins
+        let s = d.merged(&json!({"marginLeft": 0.1, "marginTop": 0.3, "marginBottom": 0.2})).unwrap();
+        assert_eq!((s.margin_left, s.margin_right, s.margin_top, s.margin_bottom), (0.3, 0.3, 0.3, 0.3));
+    }
+
     #[test]
     fn merge_validates_links_margins_and_round_trips() {
         let d = SlideSettings::default();