diff --git a/src/csg/parser.cpp b/src/csg/parser.cpp
index 53352b41e38f1e215253f1a9ea96df176d7c728b..fca91f2f4bd32ce458a70e66852e73b01c7b40c2 100644
--- a/src/csg/parser.cpp
+++ b/src/csg/parser.cpp
@@ -412,6 +412,7 @@ template <> struct action<mulmat<Dimension::D2>> {
     for (const auto &curr_obj : st.current_2d_group) {
       mulmat.group.objs.push_back(curr_obj);
     }
+    st.current_2d_group.clear();
     st.current_2d_objs.back().push_back(mulmat);
     st.current_matrices.pop_back();
   }
@@ -435,6 +436,7 @@ template <> struct action<mulmat<Dimension::D3>> {
     for (const auto &curr_obj : st.current_3d_group) {
       mulmat.group.objs.push_back(curr_obj);
     }
+    st.current_3d_group.clear();
     st.current_3d_objs.back().push_back(mulmat);
     st.current_matrices.pop_back();
   }
diff --git a/src/csg/tests/parser/boolean.t.cpp b/src/csg/tests/parser/boolean.t.cpp
index 8a563511a876d204aaa477c578d00cf0fea4201b..6b7ff2c029fd18dce1d214a75940fccd66273463 100644
--- a/src/csg/tests/parser/boolean.t.cpp
+++ b/src/csg/tests/parser/boolean.t.cpp
@@ -119,3 +119,15 @@ multmatrix([[1, 0, 0, 0.5], [0, 1, 0, 0.1], [0, 0, 1, 0], [0, 0, 0, 1]]) {
   CHECK(cone.radius2 == 0.4);
   CHECK(cone.center == false);
 }
+
+TEST_CASE("mulmat and empty group", "[csg]") {
+  auto st = *csg::parse_csg(R"(
+multmatrix([[0, 0, 1, 0], [0, 1, 0, 0], [-1, 0, 0, 0], [0, 0, 0, 1]]) {
+   cylinder($fn = 0, $fa = 12, $fs = 2, h = 200, r1 = 7, r2 = 7, center = false);
+}
+group();
+)");
+  auto un = std::get<csg::Union3D>(st.top.objs.at(1));
+
+  CHECK(un.objs.size() == 0);
+}