diff --git a/CMakeLists.txt b/CMakeLists.txt
index cebacaa..d2625d3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,7 +11,8 @@ set(libucore_VERSION ${libucore_VERSION_MAJOR}.${libucore_VERSION_MINOR}.${libuc
 
 set(CMAKE_VERBOSE_MAKEFILE ON)
 
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu99 -Wall -Wextra -Wundef -Wcast-qual -Wshadow -Wcast-align -pipe -Wno-unused-parameter -Werror=implicit-function-declaration -Winit-self -pthread")
+set(CMAKE_C_STANDARD 99)
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra -Wundef -Wcast-qual -Wshadow -Wcast-align -pipe -Wno-unused-parameter -Werror=implicit-function-declaration -Winit-self -pthread")
 add_definitions(-D_FILE_OFFSET_BITS=64)
 set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -O2 -pthread")