diff --git a/src/builtin/list.rs b/src/builtin/list.rs
index bb7bbb7..2c9a8aa 100644
--- a/src/builtin/list.rs
+++ b/src/builtin/list.rs
@@ -149,10 +149,12 @@ pub(crate) fn register(f: &mut HashMap<String, Builtin>) {
             max_args!(args, 4);
             let (mut list1, sep1, brackets) = match arg!(args, 0, "list1") {
                 Value::List(v, sep, brackets) => (v, sep, brackets),
+                Value::Map(m) => (m.entries(), ListSeparator::Comma, Brackets::None),
                 v => (vec![v], ListSeparator::Space, Brackets::None),
             };
             let (list2, sep2) = match arg!(args, 1, "list2") {
                 Value::List(v, sep, ..) => (v, sep),
+                Value::Map(m) => (m.entries(), ListSeparator::Comma),
                 v => (vec![v], ListSeparator::Space),
             };
             let sep = match arg!(
diff --git a/tests/list.rs b/tests/list.rs
index ed12465..c5b91a5 100644
--- a/tests/list.rs
+++ b/tests/list.rs
@@ -217,6 +217,11 @@ test!(
     "a {\n  color: join((a,), (b,));\n}\n",
     "a {\n  color: a, b;\n}\n"
 );
+test!(
+    join_two_maps,
+    "a {\n  color: join((c: d, e: f), (g: h, i: j));\n}\n",
+    "a {\n  color: c d, e f, g h, i j;\n}\n"
+);
 test!(bracketed_ident, "a {\n  color: [a];\n}\n");
 test!(bracketed_space_list, "a {\n  color: [a b];\n}\n");
 test!(bracketed_comma_list, "a {\n  color: [a, b];\n}\n");