diff --git a/src/interfaces/ecpg/nls.mk b/src/interfaces/ecpg/nls.mk
index 675737debfe..99957fde7b3 100644
--- a/src/interfaces/ecpg/nls.mk
+++ b/src/interfaces/ecpg/nls.mk
@@ -18,3 +18,14 @@ GETTEXT_FILES	= \
 	preproc/type.c \
 	preproc/variable.c
 GETTEXT_TRIGGERS = _ mmerror:3 ecpg_gettext ecpg_log:1
+
+
+# Without these rules, make will invoke predefined implicit rules using "lex" 
+# and "yacc", which we don't want.  The prerequisites should be exactly the 
+# same as in preproc/Makefile.
+
+$(srcdir)/preproc/preproc.c: preproc/preproc.y
+	$(MAKE) -C preproc preproc.c
+
+$(srcdir)/preproc/pgc.c: preproc/pgc.l
+	$(MAKE) -C preproc pgc.c