diff --git a/qutebrowser/browser/history.py b/qutebrowser/browser/history.py
index ca62d9e6c..2c4c1f226 100644
--- a/qutebrowser/browser/history.py
+++ b/qutebrowser/browser/history.py
@@ -40,7 +40,10 @@ class CompletionHistory(sql.SqlTable):
 
     def __init__(self, parent=None):
         super().__init__("CompletionHistory", ['url', 'title', 'last_atime'],
-                         constraints={'url': 'PRIMARY KEY'}, parent=parent)
+                         constraints={'url': 'PRIMARY KEY',
+                                      'title': 'NOT NULL',
+                                      'last_atime': 'NOT NULL'},
+                         parent=parent)
         self.create_index('CompletionHistoryAtimeIndex', 'last_atime')
 
 
@@ -50,6 +53,10 @@ class WebHistory(sql.SqlTable):
 
     def __init__(self, parent=None):
         super().__init__("History", ['url', 'title', 'atime', 'redirect'],
+                         constraints={'url': 'NOT NULL',
+                                      'title': 'NOT NULL',
+                                      'atime': 'NOT NULL',
+                                      'redirect': 'NOT NULL'},
                          parent=parent)
         self.completion = CompletionHistory(parent=self)
         if sql.Query('pragma user_version').run().value() < _USER_VERSION:
diff --git a/qutebrowser/misc/sql.py b/qutebrowser/misc/sql.py
index bfb1d1e8b..24e2035e6 100644
--- a/qutebrowser/misc/sql.py
+++ b/qutebrowser/misc/sql.py
@@ -161,8 +161,7 @@ class SqlTable(QObject):
         self._name = name
 
         constraints = constraints or {}
-        default = 'NOT NULL'
-        column_defs = ['{} {}'.format(field, constraints.get(field, default))
+        column_defs = ['{} {}'.format(field, constraints.get(field, ''))
                        for field in fields]
         q = Query("CREATE TABLE IF NOT EXISTS {name} ({column_defs})"
                   .format(name=name, column_defs=', '.join(column_defs)))