diff --git a/configure b/configure
index 2d44e8c8d..67f5b869c 100755
--- a/configure
+++ b/configure
@@ -5672,7 +5672,7 @@ if test "${with_openssl+set}" = set; then
     ;;
   *)
     specialssldir="$with_openssl"
-    CXXFLAGS="$CXXFLAGS -I$with_openssl/include"
+    CPPFLAGS="$CPPFLAGS -I$with_openssl/include"
     LDFLAGS="$LDFLAGS -L$with_openssl/lib"
     ;;
   esac
@@ -6187,7 +6187,7 @@ fi
     _cppflags=$CXXFLAGS
     _ldflags=$LDFLAGS
 
-    CXXFLAGS="-I$with_libpcap/include $CXXFLAGS"
+    CPPFLAGS="-I$with_libpcap/include $CPPFLAGS"
     LDFLAGS="-L$with_libpcap/lib $LDFLAGS"
 
     if test "${ac_cv_header_pcap_h+set}" = set; then
@@ -6405,7 +6405,7 @@ if test $have_libpcap = yes; then
     _cflags=$CXXFLAGS
     _ldflags=$LDFLAGS
 
-    CXXFLAGS="-I$LIBPCAP_INC $CXXFLAGS"
+    CPPFLAGS="-I$LIBPCAP_INC $CPPFLAGS"
     LDFLAGS="-L$LIBPCAP_LIB $LDFLAGS"
   fi
 
@@ -6493,10 +6493,10 @@ _ACEOF
 else
   if test "${LIBPCAP_INC+set}" = "set"; then
     LDFLAGS="-L$libpcapdir $_ldflags"
-    CXXFLAGS="$_cflags -I$LIBPCAP_INC"
+    CPPFLAGS="$CPPFLAGS -I$LIBPCAP_INC"
   else
     LDFLAGS="-L$libpcapdir $LDFLAGS"
-    CXXFLAGS="$CXXFLAGS -I$libpcapdir"
+    CPPFLAGS="$CPPFLAGS -I$libpcapdir"
   fi
   PCAP_DEPENDS='$(LIBPCAPDIR)/libpcap.a'
   PCAP_BUILD="pcap_build"
@@ -6530,7 +6530,7 @@ if test "${with_libpcre+set}" = set; then
     requested_included_pcre=yes
     ;;
   *)
-    CXXFLAGS="-I$with_libpcre/include $CXXFLAGS"
+    CPPFLAGS="-I$with_libpcre/include $CPPFLAGS"
     LDFLAGS="-L$with_libpcre/lib $LDFLAGS"
     have_pcre=yes
     ;;
@@ -6938,7 +6938,7 @@ fi
 if test $have_pcre != yes ; then
   subdirs="$subdirs libpcre"
 
-  CXXFLAGS="-I$LIBPCREDIR $CXXFLAGS"
+  CPPFLAGS="-I$LIBPCREDIR $CPPFLAGS"
   LIBPCRE_LIBS="$LIBPCREDIR/libpcre.a"
   PCRE_DEPENDS="$LIBPCREDIR/libpcre.a"
   PCRE_BUILD="pcre_build"
@@ -7118,7 +7118,7 @@ if test "${with_libdnet+set}" = set; then
   included)
     ;;
   *)
-    CXXFLAGS="-I$with_libdnet/include $CXXFLAGS"
+    CPPFLAGS="-I$with_libdnet/include $CPPFLAGS"
     LDFLAGS="-L$with_libdnet/lib $LDFLAGS"
     have_dnet=yes
     ;;
@@ -7131,7 +7131,7 @@ fi
 if test $have_dnet != yes ; then
   subdirs="$subdirs libdnet-stripped"
 
-  CXXFLAGS="-I$LIBDNETDIR/include $CXXFLAGS"
+  CPPFLAGS="-I$LIBDNETDIR/include $CPPFLAGS"
   LIBDNET_LIBS="$LIBDNETDIR/src/.libs/libdnet.a"
   DNET_DEPENDS="$LIBDNETDIR/src/.libs/libdnet.a"
   DNET_BUILD="dnet_build"
@@ -7166,7 +7166,7 @@ if test "${with_liblua+set}" = set; then
   yes)
   ;;
   included)
-    CXXFLAGS="-I$LIBLUADIR $CXXFLAGS"
+    CPPFLAGS="-I$LIBLUADIR $CPPFLAGS"
     LIBLUA_LIBS="$LIBLUADIR/liblua.a"
     LUA_DEPENDS="$LIBLUADIR/liblua.a"
     LUA_BUILD="lua_build"
@@ -7179,7 +7179,7 @@ if test "${with_liblua+set}" = set; then
     no_lua="yes"
   ;;
   *)
-    CXXFLAGS="-I$with_liblua/include $CXXFLAGS"
+    CPPFLAGS="-I$with_liblua/include $CPPFLAGS"
     LDFLAGS="-L$with_liblua/lib $LDFLAGS"
     have_lua=yes
   ;;
@@ -7574,7 +7574,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
   if test $have_lua != yes; then
     { echo "$as_me:$LINENO: result: no" >&5
 echo "${ECHO_T}no" >&6; }
-    CXXFLAGS="-I$LIBLUADIR $CXXFLAGS"
+    CPPFLAGS="-I$LIBLUADIR $CPPFLAGS"
     LIBLUA_LIBS="$LIBLUADIR/liblua.a"
     LUA_DEPENDS="$LIBLUADIR/liblua.a"
     LUA_BUILD="lua_build"
@@ -8393,7 +8393,7 @@ fi
 
 
 LDFLAGS="$LDFLAGS -L$NBASEDIR"
-CXXFLAGS="$CXXFLAGS -I$NBASEDIR"
+CPPFLAGS="$CPPFLAGS -I$NBASEDIR"
 LIBNBASE_LIBS="-lnbase"
 
 
@@ -8421,7 +8421,7 @@ fi
 
 
 LDFLAGS="$LDFLAGS -L$NSOCKDIR/src/"
-CXXFLAGS="$CXXFLAGS -I$NSOCKDIR/include"
+CPPFLAGS="$CPPFLAGS -I$NSOCKDIR/include"
 LIBNSOCK_LIBS="-lnsock"
 
 
diff --git a/configure.ac b/configure.ac
index ccc8cf317..54807e9b8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -215,7 +215,7 @@ AC_HELP_STRING([--with-openssl=DIR],[Use optional openssl libs and includes from
     ;;
   *)
     specialssldir="$with_openssl"
-    CXXFLAGS="$CXXFLAGS -I$with_openssl/include"
+    CPPFLAGS="$CPPFLAGS -I$with_openssl/include"
     LDFLAGS="$LDFLAGS -L$with_openssl/lib"
     ;;
   esac]
@@ -274,7 +274,7 @@ AC_HELP_STRING([--with-libpcap=included], [Always use version included with Nmap
     _cppflags=$CXXFLAGS
     _ldflags=$LDFLAGS
 
-    CXXFLAGS="-I$with_libpcap/include $CXXFLAGS"
+    CPPFLAGS="-I$with_libpcap/include $CPPFLAGS"
     LDFLAGS="-L$with_libpcap/lib $LDFLAGS"
 
     AC_CHECK_HEADER(pcap.h,[
@@ -298,7 +298,7 @@ if test $have_libpcap = yes; then
     _cflags=$CXXFLAGS
     _ldflags=$LDFLAGS
 
-    CXXFLAGS="-I$LIBPCAP_INC $CXXFLAGS"
+    CPPFLAGS="-I$LIBPCAP_INC $CPPFLAGS"
     LDFLAGS="-L$LIBPCAP_LIB $LDFLAGS"
   fi
 
@@ -335,10 +335,10 @@ if test $have_libpcap = yes; then
 else
   if test "${LIBPCAP_INC+set}" = "set"; then
     LDFLAGS="-L$libpcapdir $_ldflags"
-    CXXFLAGS="$_cflags -I$LIBPCAP_INC"
+    CPPFLAGS="$CPPFLAGS -I$LIBPCAP_INC"
   else
     LDFLAGS="-L$libpcapdir $LDFLAGS"
-    CXXFLAGS="$CXXFLAGS -I$libpcapdir"
+    CPPFLAGS="$CPPFLAGS -I$libpcapdir"
   fi
   PCAP_DEPENDS='$(LIBPCAPDIR)/libpcap.a'
   PCAP_BUILD="pcap_build"
@@ -371,7 +371,7 @@ AC_HELP_STRING([--with-libpcre=included], [Always use the version included with
     requested_included_pcre=yes
     ;;
   *)
-    CXXFLAGS="-I$with_libpcre/include $CXXFLAGS"
+    CPPFLAGS="-I$with_libpcre/include $CPPFLAGS"
     LDFLAGS="-L$with_libpcre/lib $LDFLAGS"
     have_pcre=yes
     ;;
@@ -391,7 +391,7 @@ fi
 # If we still don't have it, we use our own
 if test $have_pcre != yes ; then
   AC_CONFIG_SUBDIRS( libpcre )
-  CXXFLAGS="-I$LIBPCREDIR $CXXFLAGS"
+  CPPFLAGS="-I$LIBPCREDIR $CPPFLAGS"
   LIBPCRE_LIBS="$LIBPCREDIR/libpcre.a"
   PCRE_DEPENDS="$LIBPCREDIR/libpcre.a"
   PCRE_BUILD="pcre_build"
@@ -432,7 +432,7 @@ AC_HELP_STRING([--with-libdnet=included], [Use the libdnet version included with
   included)
     ;;
   *)
-    CXXFLAGS="-I$with_libdnet/include $CXXFLAGS"
+    CPPFLAGS="-I$with_libdnet/include $CPPFLAGS"
     LDFLAGS="-L$with_libdnet/lib $LDFLAGS"
     have_dnet=yes
     ;;
@@ -442,7 +442,7 @@ AC_HELP_STRING([--with-libdnet=included], [Use the libdnet version included with
 # If they didn't provide location, we use the included one
 if test $have_dnet != yes ; then
   AC_CONFIG_SUBDIRS( libdnet-stripped )
-  CXXFLAGS="-I$LIBDNETDIR/include $CXXFLAGS"
+  CPPFLAGS="-I$LIBDNETDIR/include $CPPFLAGS"
   LIBDNET_LIBS="$LIBDNETDIR/src/.libs/libdnet.a"
   DNET_DEPENDS="$LIBDNETDIR/src/.libs/libdnet.a"
   DNET_BUILD="dnet_build"
@@ -478,7 +478,7 @@ AC_HELP_STRING([--without-liblua], [Compile without lua (this will exclude all o
   yes)
   ;;
   included)
-    CXXFLAGS="-I$LIBLUADIR $CXXFLAGS"
+    CPPFLAGS="-I$LIBLUADIR $CPPFLAGS"
     LIBLUA_LIBS="$LIBLUADIR/liblua.a"
     LUA_DEPENDS="$LIBLUADIR/liblua.a"
     LUA_BUILD="lua_build"
@@ -491,7 +491,7 @@ AC_HELP_STRING([--without-liblua], [Compile without lua (this will exclude all o
     no_lua="yes"
   ;;
   *)
-    CXXFLAGS="-I$with_liblua/include $CXXFLAGS"
+    CPPFLAGS="-I$with_liblua/include $CPPFLAGS"
     LDFLAGS="-L$with_liblua/lib $LDFLAGS"
     have_lua=yes
   ;;
@@ -535,7 +535,7 @@ else
   # if we didn't find we use our own
   if test $have_lua != yes; then
     AC_MSG_RESULT(no) 
-    CXXFLAGS="-I$LIBLUADIR $CXXFLAGS"
+    CPPFLAGS="-I$LIBLUADIR $CPPFLAGS"
     LIBLUA_LIBS="$LIBLUADIR/liblua.a"
     LUA_DEPENDS="$LIBLUADIR/liblua.a"
     LUA_BUILD="lua_build"
@@ -667,7 +667,7 @@ NBASEDIR="nbase"
 )
 
 LDFLAGS="$LDFLAGS -L$NBASEDIR"
-CXXFLAGS="$CXXFLAGS -I$NBASEDIR"
+CPPFLAGS="$CPPFLAGS -I$NBASEDIR"
 LIBNBASE_LIBS="-lnbase"
 
 AC_SUBST(NBASEDIR)
@@ -691,7 +691,7 @@ AC_HELP_STRING([--with-libnsock=DIR], [Compile and link to libnsock in DIR]),
 )
 
 LDFLAGS="$LDFLAGS -L$NSOCKDIR/src/"
-CXXFLAGS="$CXXFLAGS -I$NSOCKDIR/include"
+CPPFLAGS="$CPPFLAGS -I$NSOCKDIR/include"
 LIBNSOCK_LIBS="-lnsock"
 
 AC_SUBST(NSOCKDIR)