diff --git a/cmake/compiler/gcc/compiler_flags.cmake b/cmake/compiler/gcc/compiler_flags.cmake
index 08b229672c4..0066ee231a1 100644
--- a/cmake/compiler/gcc/compiler_flags.cmake
+++ b/cmake/compiler/gcc/compiler_flags.cmake
@@ -119,10 +119,15 @@ set_compiler_property(TARGET compiler-cpp PROPERTY nostdincxx "-nostdinc++")
 # Required C++ flags when using gcc
 set_property(TARGET compiler-cpp PROPERTY required "-fcheck-new")
 
-# GCC compiler flags for C++ dialects
+# GCC compiler flags for C++ dialect: "register" variables and some
+# "volatile" usage generates warnings by default in standard versions
+# higher than 17 and 20 respectively.  Zephyr uses both, so turn off
+# the warnings where needed (but only on the compilers that generate
+# them, older toolchains like xcc don't understand the command line
+# flags!)
 set_property(TARGET compiler-cpp PROPERTY dialect_cpp98 "-std=c++98")
-set_property(TARGET compiler-cpp PROPERTY dialect_cpp11 "-std=c++11" "-Wno-register")
-set_property(TARGET compiler-cpp PROPERTY dialect_cpp14 "-std=c++14" "-Wno-register")
+set_property(TARGET compiler-cpp PROPERTY dialect_cpp11 "-std=c++11")
+set_property(TARGET compiler-cpp PROPERTY dialect_cpp14 "-std=c++14")
 set_property(TARGET compiler-cpp PROPERTY dialect_cpp17 "-std=c++17" "-Wno-register")
 set_property(TARGET compiler-cpp PROPERTY dialect_cpp2a "-std=c++2a"
   "-Wno-register" "-Wno-volatile")