diff --git a/init/00_InitDB.sql b/init/00_InitDB.sql
index bf720ff..ec23a24 100644
--- a/init/00_InitDB.sql
+++ b/init/00_InitDB.sql
@@ -23,8 +23,8 @@ CREATE TABLE Posts
 
 CREATE TABLE Answers (
     id              bigserial PRIMARY KEY,
-    parent          bigserial REFERENCES Posts,
-    child           bigserial REFERENCES Posts,
+    parent          bigserial REFERENCES Posts NOT NULL,
+    child           bigserial REFERENCES Posts NOT NULL,
     deleted         timestamp WITH TIME ZONE default NULL
 );