diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8159bf2..2aa29f1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,6 +11,7 @@ IF (KAZMATH_BUILD_TESTS)
     FIND_PACKAGE(PkgConfig REQUIRED)
 ENDIF (KAZMATH_BUILD_TESTS)
 
+SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=c99")
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED ON)
 set(CMAKE_C_EXTENSIONS OFF)