-CFLAGS = @TOOLKIT_DEF@ @WXDEBUG_DEFINE@ @CFLAGS@
-CPPFLAGS = @TOOLKIT_DEF@ @WXDEBUG_DEFINE@ @CXXFLAGS@ @CPPFLAGS@
+#
+# CPPFLAGS (gnu standard) is not C++ flags, but flags for the "cpp"
+# preprocessor. Unfortunately whoever wrote this now uses CPPFLAGS for
+# C++ like CFLAGS for C. :-(
+# We *must* include CPPFLAGS in both of these, to make sure that all
+# header files get found. (KB)
+
+CFLAGS = @TOOLKIT_DEF@ @CODE_GEN_FLAGS@ @WXDEBUG_DEFINE@ @CFLAGS@ @CPPFLAGS@
+CPPFLAGS = @TOOLKIT_DEF@ @CODE_GEN_FLAGS@ @WXDEBUG_DEFINE@ @CXXFLAGS@ @CPPFLAGS@