diff --git a/src/backend/utils/adt/ddlutils.c b/src/backend/utils/adt/ddlutils.c
index c4f9f86c43e..533fc8c9f9c 100644
--- a/src/backend/utils/adt/ddlutils.c
+++ b/src/backend/utils/adt/ddlutils.c
@@ -887,6 +887,17 @@ pg_get_database_ddl_internal(Oid dbid, bool pretty,
 	dbform = (Form_pg_database) GETSTRUCT(tuple);
 	dbname = pstrdup(NameStr(dbform->datname));
 
+	/*
+	 * Reject invalid databases: datconnlimit = -2 would be emitted as
+	 * CONNECTION LIMIT = -2, which fails on replay.
+	 */
+	if (database_is_invalid_form(dbform))
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot generate DDL for invalid database \"%s\"",
+						dbname),
+				 errhint("Use DROP DATABASE to drop invalid databases.")));
+
 	/*
 	 * We don't support generating DDL for system databases.  The primary
 	 * reason for this is that users shouldn't be recreating them.