diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2f56d7ce..83692e9f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -118,12 +118,11 @@ endforeach()
 # XXX - similar hints for other compilers?
 #
 if(CMAKE_C_COMPILER_ID MATCHES "GNU" OR CMAKE_C_COMPILER_ID MATCHES "Clang")
-  add_definitions(
-    "-D_U_=__attribute__((unused))"
-    "-DNGHTTP2_NORETURN=__attribute__((noreturn))"
-  )
+  set(HINT_UNUSED_PARAM   "__attribute__((unused))")
+  set(HINT_NORETURN       "__attribute__((noreturn))")
 else()
-  add_definitions(-D_U_ -DNGHTTP2_NORETURN)
+  set(HINT_UNUSED_PARAM)
+  set(HINT_NORETURN)
 endif()
 
 include(ExtractValidFlags)
diff --git a/cmakeconfig.h.in b/cmakeconfig.h.in
index d7db50f3..3e39463d 100644
--- a/cmakeconfig.h.in
+++ b/cmakeconfig.h.in
@@ -1,4 +1,10 @@
 
+/* Hint to the compiler that a function parameter is not used  */
+#define _U_ @HINT_UNUSED_PARAM@
+
+/* Hint to the compiler that a function never returns */
+#define NGHTTP2_NORETURN @HINT_NORETURN@
+
 /* Define to 1 if you have the `std::map::emplace`. */
 #cmakedefine HAVE_STD_MAP_EMPLACE 1