diff --git a/Makefile b/Makefile
index c49a328d9..39e3bbd65 100644
--- a/Makefile
+++ b/Makefile
@@ -224,7 +224,11 @@ ifndef NOFORTRAN
 	-@echo "PNOOPT      = $(FPFLAGS) -O0" >> $(NETLIB_LAPACK_DIR)/make.inc
 	-@echo "LOADOPTS    = $(FFLAGS) $(EXTRALIB)" >> $(NETLIB_LAPACK_DIR)/make.inc
 	-@echo "CC          = $(CC)" >> $(NETLIB_LAPACK_DIR)/make.inc
+ifdef INTERFACE64
+	-@echo "CFLAGS      = $(CFLAGS) -DHAVE_LAPACK_CONFIG_H  -DLAPACK_ILP64" >> $(NETLIB_LAPACK_DIR)/make.inc
+else
 	-@echo "CFLAGS      = $(CFLAGS)" >> $(NETLIB_LAPACK_DIR)/make.inc
+endif
 	-@echo "ARCH        = $(AR)" >> $(NETLIB_LAPACK_DIR)/make.inc
 	-@echo "ARCHFLAGS   = -ru" >> $(NETLIB_LAPACK_DIR)/make.inc
 	-@echo "RANLIB      = $(RANLIB)" >> $(NETLIB_LAPACK_DIR)/make.inc