diff --git a/tsl/src/build-defs.cmake b/tsl/src/build-defs.cmake
index bd526c750da..c36252ff334 100644
--- a/tsl/src/build-defs.cmake
+++ b/tsl/src/build-defs.cmake
@@ -2,6 +2,7 @@
 set(CMAKE_C_VISIBILITY_PRESET "hidden")
 
 if (UNIX)
+  set(CMAKE_C_STANDARD 11)
   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -L${PG_LIBDIR}")
   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -L${PG_LIBDIR}")
   set(CMAKE_C_FLAGS "${PG_CFLAGS} ${CMAKE_C_FLAGS}")