diff --git a/wtforms_sqlalchemy/orm.py b/wtforms_sqlalchemy/orm.py
index f1fefb6..5a68fd3 100644
--- a/wtforms_sqlalchemy/orm.py
+++ b/wtforms_sqlalchemy/orm.py
@@ -115,11 +115,6 @@ def convert(self, model, mapper, prop, field_args, db_session=None):
 
             kwargs['default'] = default
 
-            if column.nullable:
-                kwargs['validators'].append(validators.Optional())
-            else:
-                kwargs['validators'].append(validators.Required())
-
             converter = self.get_converter(column)
         else:
             # We have a property with a direction.
@@ -153,40 +148,53 @@ class ModelConverter(ModelConverterBase):
     def __init__(self, extra_converters=None, use_mro=True):
         super(ModelConverter, self).__init__(extra_converters, use_mro=use_mro)
 
+    @classmethod
+    def _nullable_required(cls, column, field_args, **extra):
+        if column.nullable:
+            field_args['validators'].append(validators.Optional())
+        else:
+            field_args['validators'].append(validators.Required())
+
     @classmethod
     def _string_common(cls, column, field_args, **extra):
         if isinstance(column.type.length, int) and column.type.length:
             field_args['validators'].append(validators.Length(max=column.type.length))
 
     @converts('String')  # includes Unicode
-    def conv_String(self, field_args, **extra):
-        self._string_common(field_args=field_args, **extra)
+    def conv_String(self, column, field_args, **extra):
+        self._string_common(column=column, field_args=field_args, **extra)
+        self._nullable_required(column=column, field_args=field_args, **extra)
         return wtforms_fields.StringField(**field_args)
 
     @converts('Text', 'LargeBinary', 'Binary')  # includes UnicodeText
-    def conv_Text(self, field_args, **extra):
-        self._string_common(field_args=field_args, **extra)
+    def conv_Text(self, column, field_args, **extra):
+        self._string_common(column=column, field_args=field_args, **extra)
+        self._nullable_required(column=column, field_args=field_args, **extra)
         return wtforms_fields.TextAreaField(**field_args)
 
     @converts('Boolean', 'dialects.mssql.base.BIT')
-    def conv_Boolean(self, field_args, **extra):
+    def conv_Boolean(self, column, field_args, **extra):
         return wtforms_fields.BooleanField(**field_args)
 
     @converts('Date')
-    def conv_Date(self, field_args, **extra):
+    def conv_Date(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         return wtforms_fields.DateField(**field_args)
 
     @converts('DateTime')
-    def conv_DateTime(self, field_args, **extra):
+    def conv_DateTime(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         return wtforms_fields.DateTimeField(**field_args)
 
     @converts('Enum')
     def conv_Enum(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         field_args['choices'] = [(e, e) for e in column.type.enums]
         return wtforms_fields.SelectField(**field_args)
 
     @converts('Integer')  # includes BigInteger and SmallInteger
     def handle_integer_types(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         unsigned = getattr(column.type, 'unsigned', False)
         if unsigned:
             field_args['validators'].append(validators.NumberRange(min=0))
@@ -194,39 +202,45 @@ def handle_integer_types(self, column, field_args, **extra):
 
     @converts('Numeric')  # includes DECIMAL, Float/FLOAT, REAL, and DOUBLE
     def handle_decimal_types(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         # override default decimal places limit, use database defaults instead
         field_args.setdefault('places', None)
         return wtforms_fields.DecimalField(**field_args)
 
     @converts('dialects.mysql.types.YEAR', 'dialects.mysql.base.YEAR')
-    def conv_MSYear(self, field_args, **extra):
+    def conv_MSYear(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         field_args['validators'].append(validators.NumberRange(min=1901, max=2155))
         return wtforms_fields.StringField(**field_args)
 
     @converts('dialects.postgresql.base.INET')
-    def conv_PGInet(self, field_args, **extra):
+    def conv_PGInet(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         field_args.setdefault('label', 'IP Address')
         field_args['validators'].append(validators.IPAddress())
         return wtforms_fields.StringField(**field_args)
 
     @converts('dialects.postgresql.base.MACADDR')
-    def conv_PGMacaddr(self, field_args, **extra):
+    def conv_PGMacaddr(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         field_args.setdefault('label', 'MAC Address')
         field_args['validators'].append(validators.MacAddress())
         return wtforms_fields.StringField(**field_args)
 
     @converts('dialects.postgresql.base.UUID')
-    def conv_PGUuid(self, field_args, **extra):
+    def conv_PGUuid(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         field_args.setdefault('label', 'UUID')
         field_args['validators'].append(validators.UUID())
         return wtforms_fields.StringField(**field_args)
 
     @converts('MANYTOONE')
-    def conv_ManyToOne(self, field_args, **extra):
+    def conv_ManyToOne(self, column, field_args, **extra):
         return QuerySelectField(**field_args)
 
     @converts('MANYTOMANY', 'ONETOMANY')
-    def conv_ManyToMany(self, field_args, **extra):
+    def conv_ManyToMany(self, column, field_args, **extra):
+        self._nullable_required(column=column, field_args=field_args, **extra)
         return QuerySelectMultipleField(**field_args)