diff --git a/src/backend/nodes/Makefile b/src/backend/nodes/Makefile
index 1a0d5b93140..79ce0a532fe 100644
--- a/src/backend/nodes/Makefile
+++ b/src/backend/nodes/Makefile
@@ -12,6 +12,8 @@ subdir = src/backend/nodes
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
+override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
+
 OBJS = \
 	bitmapset.o \
 	copyfuncs.o \