diff --git a/include/libcopp/utils/config/compiler_features.h b/include/libcopp/utils/config/compiler_features.h
index 0b44b11..9a26b76 100644
--- a/include/libcopp/utils/config/compiler_features.h
+++ b/include/libcopp/utils/config/compiler_features.h
@@ -76,7 +76,7 @@
 # undef UTIL_CONFIG_COMPILER_IS_zOS
 # define UTIL_CONFIG_COMPILER_IS_zOS 1
 
-#elif defined(__ibmxl__) || (defined(__IBMCPP__) && !defined(__COMPILER_VER__) && __IBMCPP__ >= 800)
+#elif defined(__IBMCPP__) && !defined(__COMPILER_VER__) && __IBMCPP__ >= 800
 # undef UTIL_CONFIG_COMPILER_IS_XL
 # define UTIL_CONFIG_COMPILER_IS_XL 1
 
@@ -637,8 +637,6 @@
 
 #  if defined(UTIL_CONFIG_COMPILER_CXX_NULLPTR) && UTIL_CONFIG_COMPILER_CXX_NULLPTR
 #    define UTIL_CONFIG_NULLPTR nullptr
-#  elif UTIL_CONFIG_COMPILER_IS_GNU
-#    define UTIL_CONFIG_NULLPTR __null
 #  else
 #    define UTIL_CONFIG_NULLPTR 0
 #  endif