diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8be234c49..8ce55eff2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -94,7 +94,7 @@ endif()
 set(JUDY_LIBRARIES "Judy")
 
 # Standard FLAGS
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu99")
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu11")
 if(NOT APPLE)
     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -pthread")
 endif()
diff --git a/src/if-netmap-linux.c b/src/if-netmap-linux.c
index fe563293d..2965e0da8 100644
--- a/src/if-netmap-linux.c
+++ b/src/if-netmap-linux.c
@@ -94,7 +94,7 @@ fetch_stats64(struct rtnl_link_stats64 *rtlstats64, char const *ifname, int nlrt
 			} err;
 		} u;
 	} nlresp;
-	_Static_assert(sizeof(nlresp.u.ans) >= sizeof(nlresp.u.err));
+	static_assert(sizeof(nlresp.u.ans) >= sizeof(nlresp.u.err), "ans is at least as large as err");
 	static const size_t ans_size = offsetof(struct nlresp, u.ans) + sizeof(nlresp.u.ans);
 	static const size_t err_size = offsetof(struct nlresp, u.err) + sizeof(nlresp.u.err);