diff --git a/src/backend/replication/Makefile b/src/backend/replication/Makefile
index 3fe490e580..9d9ec87c9a 100644
--- a/src/backend/replication/Makefile
+++ b/src/backend/replication/Makefile
@@ -12,6 +12,8 @@ subdir = src/backend/replication
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
+override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
+
 OBJS = walsender.o walreceiverfuncs.o walreceiver.o basebackup.o \
 	repl_gram.o syncrep.o