diff --git a/cmake/modules/AddCompilerFlags.cmake b/cmake/modules/AddCompilerFlags.cmake
--- a/cmake/modules/AddCompilerFlags.cmake
+++ b/cmake/modules/AddCompilerFlags.cmake
@@ -4,7 +4,7 @@
 include(SanitizeHelper)
 
 function(check_compiler_flag RESULT LANGUAGE FLAG)
-	sanitize_variable("have_${LANGUAGE}_" ${FLAG} TEST_NAME)
+	sanitize_c_cxx_definition("have_${LANGUAGE}_" ${FLAG} TEST_NAME)
 
 	if("${LANGUAGE}" STREQUAL "C")
 		CHECK_C_COMPILER_FLAG(${FLAG} ${TEST_NAME})
@@ -99,7 +99,7 @@
 # is a workaround that allow for testing the linker flags.
 function(add_linker_flag)
 	foreach(f ${ARGN})
-		sanitize_variable("have_linker_" ${f} FLAG_IS_SUPPORTED)
+		sanitize_c_cxx_definition("have_linker_" ${f} FLAG_IS_SUPPORTED)
 
 		# Some linkers (e.g.: Clang) will issue a -Wunused-command-line-argument
 		# warning when an unknown linker flag is set.
diff --git a/cmake/modules/SanitizeHelper.cmake b/cmake/modules/SanitizeHelper.cmake
--- a/cmake/modules/SanitizeHelper.cmake
+++ b/cmake/modules/SanitizeHelper.cmake
@@ -1,3 +1,8 @@
+macro(_sanitize REPLACEMENT_REGEX REPLACEMENT_STRING RAW_VAR SANITIZED_VAR)
+	string(REGEX REPLACE
+		"${REPLACEMENT_REGEX}" "${REPLACEMENT_STRING}" ${SANITIZED_VAR} "${RAW_VAR}")
+endmacro()
+
 # Sanitize a variable according to cmake rules
 # https://cmake.org/cmake/help/v3.10/manual/cmake-language.7.html#variable-references
 # The NUL and ';' characters cannot be escaped in this context (see CMP0053)
@@ -14,6 +19,14 @@
 	# rather to replace them with a known supported one, here '_' is chosen.
 	# Not: this could lead to name collision in some rare case. These case can
 	# be handled manually by using a different prefix.
-	string(REGEX REPLACE
-		"([^a-zA-Z0-9/_.+-])" "_" ${SANITIZED_VAR} "${PREFIX}${RAW_VAR}")
+	_sanitize("([^a-zA-Z0-9/_.+-])" "_" "${PREFIX}${RAW_VAR}" ${SANITIZED_VAR})
+endmacro()
+
+# Sanitize a variable intended to be used in a C/CXX #define statement.
+# This is useful when using CHECK_<C|CXX>_COMPILER_FLAG or similar functions.
+macro(sanitize_c_cxx_definition PREFIX RAW_VAR SANITIZED_VAR)
+	# Only allow for alphanum chars plus underscore. This will prevent the
+	# compiler to issue a warning like:
+	# `ISO C99 requires whitespace after the macro name [-Wc99-extensions]`
+	_sanitize("([^a-zA-Z0-9_])" "_" "${PREFIX}${RAW_VAR}" ${SANITIZED_VAR})
 endmacro()