diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 0258d9ace3c..bd86de53c67 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -402,7 +402,7 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 	offsetof(struct pg_conn, oauth_scope)},
 
 	{"sslkeylogfile", NULL, NULL, NULL,
-		"SSL-Key-Log-File", "", 0,	/* sizeof("") = 0 */
+		"SSL-Key-Log-File", "D", 64,
 	offsetof(struct pg_conn, sslkeylogfile)},
 
 	/* Terminating entry --- MUST BE LAST */