--- a/src/test/regress/pg_regress.c
+++ b/src/test/regress/pg_regress.c
@@ -465,7 +465,7 @@ replace_stringInfo(StringInfo string, const char *replace, const char *replaceme

        while ((ptr = strstr(string->data, replace)) != NULL)
        {
-               char       *dup = pg_strdup(string->data);
+              char       *dup = pnstrdup(string->data, string->maxlen);
                size_t          pos = ptr - string->data;

                string->len = pos;