diff --git a/src/backend/utils/sort/Makefile b/src/backend/utils/sort/Makefile
index f46ce41610..370b12cee6 100644
--- a/src/backend/utils/sort/Makefile
+++ b/src/backend/utils/sort/Makefile
@@ -12,6 +12,8 @@ subdir = src/backend/utils/sort
 top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
+override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
+
 OBJS = logtape.o sortsupport.o tuplesort.o tuplestore.o
 
 tuplesort.o: qsort_tuple.c