--- a/configure.in
+++ b/configure.in
@@ -95,7 +95,7 @@ CF_PROG_EXT
 CF_LIB_PREFIX(LIB_PREFIX)
 AC_PROG_LN_S
 
-CF_BUILD_CC([-I$(INCDIR)],[])
+CF_BUILD_CC([-I$(INCDIR) ${CPPFLAGS}],[])
 
 #### initialize $ac_includes_default
 AC_CHECK_DECL(exit)
--- a/configure
+++ b/configure
@@ -3199,7 +3199,7 @@ if test "$cross_compiling" = yes ; then
 
 	# defaults that we might want to override
 	: ${BUILD_CFLAGS:=''}
-	: ${BUILD_CPPFLAGS:='-I$(INCDIR)'}
+	: ${BUILD_CPPFLAGS:='-I$(INCDIR) ${CPPFLAGS}'}
 	: ${BUILD_LDFLAGS:=''}
 	: ${BUILD_LIBS:=''}
 	: ${BUILD_EXEEXT:='$x'}
@@ -3380,7 +3380,7 @@ else
 	: ${BUILD_CC:='${CC}'}
 	: ${BUILD_CPP:='${CPP}'}
 	: ${BUILD_CFLAGS:='${CFLAGS}'}
-	: ${BUILD_CPPFLAGS:='-I$(INCDIR)'}
+	: ${BUILD_CPPFLAGS:='-I$(INCDIR) ${CPPFLAGS}'}
 	: ${BUILD_LDFLAGS:='${LDFLAGS}'}
 	: ${BUILD_LIBS:=''${LIBS}''}
 	: ${BUILD_EXEEXT:='$x'}
