diff --git a/meson.build b/meson.build
index 80893ab..5f733af 100644
--- a/meson.build
+++ b/meson.build
@@ -210,6 +210,7 @@
         executable(
             'test_entity_manager',
             'test/test_entity-manager.cpp',
+            'src/Expression.cpp',
             'src/Utils.cpp',
             cpp_args: test_boost_args,
             dependencies: [