diff --git a/config/CONFIG_SITE.sun4 b/config/CONFIG_SITE.sun4
index c0f19235f..f9894615a 100644
--- a/config/CONFIG_SITE.sun4
+++ b/config/CONFIG_SITE.sun4
@@ -23,6 +23,8 @@ CXXCMPLR=NORMAL
 #ANSI=GCC
 #STANDARD=GCC
 #CPLUSPLUS=G++
+#Note: if CPLUSPLUS is empty then C++ src codes are not built
+CPLUSPLUS=
 
 # Special C library requirements
 #SPECIAL_LANG = /usr/lang/SC3.0.1