diff --git a/CMakeLists.txt b/CMakeLists.txt
index c28b2c657..62abd54a7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -114,7 +114,13 @@ if(PROFILE)
   set(FLAGS "${FLAGS} -pg " CACHE STRING "Compilation flags" FORCE)
 endif()
 
-set(CMAKE_C_FLAGS "${FLAGS}")
+if(USE_C99)
+  message(STATUS "Using C99 standard")
+  set(CMAKE_C_FLAGS "-std=c99 -D_GNU_SOURCE=1 ${FLAGS}")
+else()
+  set(CMAKE_C_FLAGS "${FLAGS}")
+endif()
+
 set(CMAKE_C_FLAGS_DEBUG "${DEBUG_FLAGS} -DSS_DEBUG -DLOG_ASSERT")
 set(CMAKE_C_FLAGS_RELEASE "")
 set(CMAKE_C_FLAGS_RELWITHDEBINFO "-ggdb")
diff --git a/cmake/macros.cmake b/cmake/macros.cmake
index b78502cf9..d7921f1c4 100644
--- a/cmake/macros.cmake
+++ b/cmake/macros.cmake
@@ -20,6 +20,9 @@ endmacro()
 
 macro(set_variables)
 
+  # Use C99
+  set(USE_C99 FALSE CACHE BOOL "Use C99 standard")
+
   # hostname or IP address of MaxScale's host
   set(TEST_HOST "127.0.0.1" CACHE STRING "hostname or IP address of MaxScale's host")