diff --git a/src/compare/compare_field.rs b/src/compare/compare_field.rs
index e56e316..27a7922 100644
--- a/src/compare/compare_field.rs
+++ b/src/compare/compare_field.rs
@@ -424,7 +424,7 @@ pub(crate) fn compare_property_list_of_list_of_list_of_ast_nodes<
     's,
     'x,
     R,
-    RG: Fn(R) -> Option<&'b Vec<Vec<Object<'s>>>>,
+    RG: Fn(R) -> Option<&'b Vec<(Option<Vec<Object<'s>>>, Vec<Object<'s>>)>>,
 >(
     source: &'s str,
     emacs: &'b Token<'s>,
@@ -461,10 +461,41 @@ pub(crate) fn compare_property_list_of_list_of_list_of_ast_nodes<
     };
 
     // Iterate the outer lists
-    for (value, rust_value) in value.iter().zip(rust_value.iter()) {
-        // Assert the middle list is a length of 1 because I've never seen it any other way.
-        let value = value.as_list()?;
-        if value.len() != 1 {
+    for (value, (rust_optional, rust_value)) in value.iter().zip(rust_value.iter()) {
+        let mut middle_value = value.as_list()?.iter();
+        // First element of middle list is the mandatory value (the value past the colon).
+        let mandatory_value = middle_value.next();
+        let mandatory_value = match mandatory_value {
+            Some(mandatory_value) => mandatory_value,
+            None => {
+                let this_status = DiffStatus::Bad;
+                let message = Some(format!(
+                    "{} mismatch (emacs != rust) {:?} != {:?}",
+                    emacs_field, value, rust_value
+                ));
+                return Ok(ComparePropertiesResult::SelfChange(this_status, message));
+            }
+        };
+        let mut child_status: Vec<DiffEntry<'b, 's>> = Vec::with_capacity(rust_value.len());
+
+        // Compare optional value
+        if let Some(rust_optional) = rust_optional {
+            if rust_optional.len() != middle_value.len() {
+                let this_status = DiffStatus::Bad;
+                let message = Some(format!(
+                    "{} mismatch (emacs != rust) {:?} != {:?}",
+                    emacs_field, value, rust_value
+                ));
+                return Ok(ComparePropertiesResult::SelfChange(this_status, message));
+            }
+            for (e, r) in middle_value.zip(rust_optional) {
+                child_status.push(compare_ast_node(source, e, r.into())?);
+            }
+        }
+
+        // Compare mandatory value
+        let mandatory_value = mandatory_value.as_list()?;
+        if rust_value.len() != mandatory_value.len() {
             let this_status = DiffStatus::Bad;
             let message = Some(format!(
                 "{} mismatch (emacs != rust) {:?} != {:?}",
@@ -472,14 +503,7 @@ pub(crate) fn compare_property_list_of_list_of_list_of_ast_nodes<
             ));
             return Ok(ComparePropertiesResult::SelfChange(this_status, message));
         }
-        // Drill past the middle list to the inner list.
-        let value = value
-            .first()
-            .expect("The above if-statement asserts this exists.");
-        let value = value.as_list()?;
-        // Compare inner lists
-        let mut child_status: Vec<DiffEntry<'b, 's>> = Vec::with_capacity(rust_value.len());
-        for (e, r) in value.iter().zip(rust_value) {
+        for (e, r) in mandatory_value.iter().zip(rust_value) {
             child_status.push(compare_ast_node(source, e, r.into())?);
         }
         let diff_scope = artificial_owned_diff_scope(emacs_field, child_status)?;