diff --git a/common/CMakeLists.txt b/common/CMakeLists.txt
index 145dfda..59dff7b 100644
--- a/common/CMakeLists.txt
+++ b/common/CMakeLists.txt
@@ -1,5 +1,11 @@
+if(USE_INCLUDED_ZLIB)
+  add_subdirectory(zlib)
+
+  set(ZLIB_INCLUDE_DIRS ${CMAKE_SOURCE_DIR}/common/zlib)
+  set(ZLIB_LIBRARIES zlib)
+endif()
+
 add_subdirectory(os)
-add_subdirectory(zlib)
 add_subdirectory(rdr)
 add_subdirectory(network)
 add_subdirectory(Xregion)