--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,7 @@ PG91 = $(shell $(PG_CONFIG) --version |
 ifeq ($(PG91),yes)
 all: sql/$(EXTENSION)--$(EXTVERSION).sql
 
-sql/$(EXTENSION)--$(EXTVERSION).sql: sql/tables/*.sql sql/functions/*.sql sql/triggers/*.sql
+sql/$(EXTENSION)--$(EXTVERSION).sql: $(sort $(wildcard sql/tables/*.sql)) $(sort $(wildcard sql/functions/*.sql)) $(sort $(wildcard sql/triggers/*.sql))
 	cat $^ > $@
 
 DATA = $(wildcard updates/*--*.sql) sql/$(EXTENSION)--$(EXTVERSION).sql
