diff --git a/contrib/spi/refint.c b/contrib/spi/refint.c
index cbef463230a..413411c173d 100644
--- a/contrib/spi/refint.c
+++ b/contrib/spi/refint.c
@@ -480,7 +480,8 @@ check_foreign_key(PG_FUNCTION_ARGS)
 						nv = SPI_getvalue(newtuple, tupdesc, fn);
 
 						appendStringInfo(&sql, " %s = %s ",
-										 args2[k], quote_literal_cstr(nv));
+										 args2[k],
+										 nv ? quote_literal_cstr(nv) : "NULL");
 						if (k < nkeys)
 							appendStringInfoString(&sql, ", ");
 					}