--- a/GDALmake.opt.in	2020-05-25 15:09:29.892069150 +0200
+++ b/GDALmake.opt.in	2020-05-25 15:09:54.164285244 +0200
@@ -74,7 +74,7 @@ INST_DOCS	=	@htmldir@
 INST_MAN	=	@mandir@
 INST_WEB	=	$(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)