diff --git a/src/wasm/mod.rs b/src/wasm/mod.rs
index c790977..3ba6002 100644
--- a/src/wasm/mod.rs
+++ b/src/wasm/mod.rs
@@ -63,6 +63,8 @@ mod underline;
 mod verbatim;
 mod verse_block;
 
+pub use additional_property::AdditionalProperties;
+pub use additional_property::AdditionalPropertyValue;
 pub use ast_node::WasmAstNode;
 pub use document::WasmDocument;
 pub(crate) use headline::WasmHeadline;
diff --git a/src/wasm_test/compare.rs b/src/wasm_test/compare.rs
index c6a6dda..1336740 100644
--- a/src/wasm_test/compare.rs
+++ b/src/wasm_test/compare.rs
@@ -6,6 +6,8 @@ use crate::compare::get_property_quoted_string;
 use crate::compare::ElispFact;
 use crate::compare::EmacsField;
 use crate::compare::Token;
+use crate::wasm::AdditionalProperties;
+use crate::wasm::AdditionalPropertyValue;
 use crate::wasm::WasmAstNode;
 use crate::wasm::WasmDocument;
 use crate::wasm::WasmHeadline;
@@ -416,3 +418,35 @@ fn wasm_compare_standard_properties<'b, 's>(
     result.children.push(layer);
     Ok(result)
 }
+
+fn wasm_compare_additional_properties<'b, 's>(
+    source: &'s str,
+    emacs: &'b Token<'s>,
+    wasm: &AdditionalProperties<'_, '_>,
+) -> Result<WasmDiffResult<'s>, Box<dyn std::error::Error>> {
+    let mut result = WasmDiffResult::default();
+    let mut layer = WasmDiffResult::default();
+    layer.name = "additional-properties".into();
+
+    for (property_name, property_value) in wasm.properties.iter() {
+        let emacs_property_name = format!(":{property_name}", property_name = property_name);
+        match property_value {
+            AdditionalPropertyValue::SingleString(wasm_value) => {
+                layer.extend(wasm_compare_property_quoted_string(
+                    source,
+                    emacs,
+                    wasm,
+                    &emacs_property_name,
+                    |_| Some(wasm_value),
+                )?)?;
+            }
+            // TODO: similar to compare_affiliated_keywords
+            AdditionalPropertyValue::ListOfStrings(_) => todo!(),
+            AdditionalPropertyValue::OptionalPair { optval, val } => todo!(),
+            AdditionalPropertyValue::ObjectTree(_) => todo!(),
+        }
+    }
+
+    result.children.push(layer);
+    Ok(result)
+}
diff --git a/src/wasm_test/macros.rs b/src/wasm_test/macros.rs
index 0712196..5e0f181 100644
--- a/src/wasm_test/macros.rs
+++ b/src/wasm_test/macros.rs
@@ -68,6 +68,8 @@ macro_rules! wasm_compare {
 
                 }
             }
+
+            result.extend(wasm_compare_additional_properties($source, $emacs, &$wasm.additional_properties)?)?;
         }
 
         {