diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a6ff58..74a87fa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,9 +29,11 @@ SET_TARGET_PROPERTIES(ubox-static PROPERTIES OUTPUT_NAME ubox)
 
 SET(LIBS)
 CHECK_FUNCTION_EXISTS(clock_gettime HAVE_GETTIME)
-IF(NOT HAVE_GETTIME)
+CHECK_FUNCTION_EXISTS(shm_open HAVE_SHM)
+IF(NOT HAVE_GETTIME OR NOT HAVE_SHM)
 	CHECK_LIBRARY_EXISTS(rt clock_gettime "" NEED_GETTIME)
-	IF(NEED_GETTIME)
+	CHECK_LIBRARY_EXISTS(rt shm_open "" NEED_SHM)
+	IF(NEED_GETTIME OR NEED_SHM)
 		TARGET_LINK_LIBRARIES(ubox rt)
 	ENDIF()
 ENDIF()