diff -rup a/GDALmake.opt.in b/GDALmake.opt.in
--- a/GDALmake.opt.in	2018-05-04 18:05:45.000000000 +0200
+++ b/GDALmake.opt.in	2018-05-14 09:47:11.178524546 +0200
@@ -67,7 +67,7 @@ INST_DOCS	=	@exec_prefix@/doc
 INST_MAN	=	@mandir@
 INST_HTML	=	$(HOME)/www/gdal
 
-CPPFLAGS	:= @CPPFLAGS@ -I$(GDAL_ROOT)/port @EXTRA_INCLUDES@ -DGDAL_COMPILATION
+CPPFLAGS	:= @CPPFLAGS@ -I$(GDAL_ROOT)/gcore -I$(GDAL_ROOT)/port @EXTRA_INCLUDES@ -DGDAL_COMPILATION
 CFLAGS		= @CFLAGS@ @C_WFLAGS@ $(USER_DEFS)
 CXXFLAGS	= @CXXFLAGS@ @CXX_WFLAGS@ $(USER_DEFS)
 CFLAGS_NOFTRAPV          = @CFLAGS_NOFTRAPV@ @C_WFLAGS@ $(USER_DEFS)