diff --git a/crlcore/src/CMakeLists.txt b/crlcore/src/CMakeLists.txt
index 5df690d4..4d831b94 100644
--- a/crlcore/src/CMakeLists.txt
+++ b/crlcore/src/CMakeLists.txt
@@ -1,5 +1,9 @@
 add_subdirectory(ccore)
 add_subdirectory(LibraryManager)
 add_subdirectory(pyCRL)
-add_subdirectory(cyclop)
-add_subdirectory(x2y)
+
+if(CMAKE_BUILD_TYPE EQUAL "Release")
+  add_subdirectory(x2y)
+  add_subdirectory(cyclop)
+endif()
+