diff --git a/accountant/api/models/accounts.py b/accountant/api/models/accounts.py
index a0e1b4b..897e949 100644
--- a/accountant/api/models/accounts.py
+++ b/accountant/api/models/accounts.py
@@ -14,9 +14,6 @@
     You should have received a copy of the GNU Affero General Public License
     along with Accountant.  If not, see <http://www.gnu.org/licenses/>.
 """
-from sqlalchemy import func, case, literal_column
-from sqlalchemy.orm import validates
-
 from accountant import db
 
 from .operations import Operation
@@ -35,17 +32,17 @@ class Account(db.Model):
     def query(cls, begin=None, end=None):
         status_query = db.session.query(
             Operation.account_id,
-            func.sum(Operation.value).label("future"),
-            func.sum(
-                case(
+            db.func.sum(Operation.value).label("future"),
+            db.func.sum(
+                db.case(
                     [(Operation.pointed,
                       Operation.value)],
                     else_=0
                 )
             ).label("pointed"),
-            func.sum(
-                case(
-                    [(Operation.operation_date <= func.current_date(),
+            db.func.sum(
+                db.case(
+                    [(Operation.operation_date <= db.func.current_date(),
                       Operation.value)],
                     else_=0
                 )
@@ -57,19 +54,21 @@ class Account(db.Model):
         if begin and end:
             balance_query = db.session.query(
                 Operation.account_id,
-                func.sum(
-                    case(
-                        [(func.sign(Operation.value) == -1, Operation.value)],
+                db.func.sum(
+                    db.case(
+                        [(db.func.sign(Operation.value) == -1,
+                          Operation.value)],
                         else_=0
                     )
                 ).label("expenses"),
-                func.sum(
-                    case(
-                        [(func.sign(Operation.value) == 1, Operation.value)],
+                db.func.sum(
+                    db.case(
+                        [(db.func.sign(Operation.value) == 1,
+                          Operation.value)],
                         else_=0
                     )
                 ).label("revenues"),
-                func.sum(Operation.value).label("balance")
+                db.func.sum(Operation.value).label("balance")
             ).filter(
                 Operation.operation_date >= str(begin),
                 Operation.operation_date <= str(end)
@@ -81,12 +80,18 @@ class Account(db.Model):
                 cls.id,
                 cls.name,
                 cls.authorized_overdraft,
-                func.coalesce(status_query.c.current, 0).label('current'),
-                func.coalesce(status_query.c.pointed, 0).label('pointed'),
-                func.coalesce(status_query.c.future, 0).label('future'),
-                func.coalesce(balance_query.c.expenses, 0).label('expenses'),
-                func.coalesce(balance_query.c.revenues, 0).label('revenues'),
-                func.coalesce(balance_query.c.balance, 0).label('balance'),
+                db.func.coalesce(
+                    status_query.c.current, 0).label('current'),
+                db.func.coalesce(
+                    status_query.c.pointed, 0).label('pointed'),
+                db.func.coalesce(
+                    status_query.c.future, 0).label('future'),
+                db.func.coalesce(
+                    balance_query.c.expenses, 0).label('expenses'),
+                db.func.coalesce(
+                    balance_query.c.revenues, 0).label('revenues'),
+                db.func.coalesce(
+                    balance_query.c.balance, 0).label('balance'),
             ).outerjoin(
                 status_query, status_query.c.account_id == cls.id
             ).outerjoin(
@@ -97,19 +102,19 @@ class Account(db.Model):
                 cls.id,
                 cls.name,
                 cls.authorized_overdraft,
-                func.coalesce(status_query.c.current, 0).label('current'),
-                func.coalesce(status_query.c.pointed, 0).label('pointed'),
-                func.coalesce(status_query.c.future, 0).label('future'),
-                literal_column("0").label('expenses'),
-                literal_column("0").label('revenues'),
-                literal_column("0").label('balance'),
+                db.func.coalesce(status_query.c.current, 0).label('current'),
+                db.func.coalesce(status_query.c.pointed, 0).label('pointed'),
+                db.func.coalesce(status_query.c.future, 0).label('future'),
+                db.literal_column("0").label('expenses'),
+                db.literal_column("0").label('revenues'),
+                db.literal_column("0").label('balance'),
             ).outerjoin(
                 status_query, status_query.c.account_id == cls.id
             )
 
         return query.order_by(cls.name)
 
-    @validates('authorized_overdraft')
+    @db.validates('authorized_overdraft')
     def validate_authorized_overdraft(self, key, authorized_overdraft):
         assert authorized_overdraft <= 0
 
diff --git a/accountant/api/models/operations.py b/accountant/api/models/operations.py
index 26b1312..b6ae971 100644
--- a/accountant/api/models/operations.py
+++ b/accountant/api/models/operations.py
@@ -18,9 +18,6 @@ from datetime import date
 
 import arrow
 
-from sqlalchemy import func, case, desc, true, false, text
-from sqlalchemy.orm import column_property
-
 from accountant import db
 
 
@@ -31,7 +28,7 @@ class Operation(db.Model):
         db.Date,
         nullable=False,
         default=date.today,
-        server_default=func.current_date(),
+        server_default=db.func.current_date(),
         index=True
     )
     label = db.Column(db.String(500), nullable=False)
@@ -59,32 +56,37 @@ class Operation(db.Model):
         db.Boolean,
         nullable=False,
         default=False,
-        server_default=false()
+        server_default=db.false()
     )
 
     confirmed = db.Column(
         db.Boolean,
         nullable=False,
         default=True,
-        server_default=true()
+        server_default=db.true()
     )
 
     canceled = db.Column(
         db.Boolean,
         nullable=False,
         default=False,
-        server_default=false()
+        server_default=db.false()
     )
 
-    sold = column_property(
-        func.sum(
-            case(
-                whens={canceled: text("0")},
+    sold = db.column_property(
+        db.func.sum(
+            db.case(
+                whens={canceled: db.text("0")},
                 else_=value
             )
         ).over(
             partition_by=[account_id],
-            order_by=["operation_date", desc("value"), desc("label"), id]
+            order_by=[
+                "operation_date",
+                db.desc("value"),
+                db.desc("label"),
+                id
+            ]
         ).label("sold")
     )
 
@@ -125,7 +127,7 @@ class Operation(db.Model):
         ).join(
             base_query, base_query.c.id == cls.id
         ).order_by(
-            desc(cls.operation_date),
+            db.desc(cls.operation_date),
             cls.value,
             cls.label,
         )
@@ -147,13 +149,13 @@ class Operation(db.Model):
 
         query = db.session.query(
             cls.category,
-            func.sum(
-                case([(func.sign(cls.value) == -1, cls.value)], else_=0)
+            db.func.sum(
+                db.case([(db.func.sign(cls.value) == -1, cls.value)], else_=0)
             ).label("expenses"),
-            func.sum(
-                case([(func.sign(cls.value) == 1, cls.value)], else_=0)
+            db.func.sum(
+                db.case([(db.func.sign(cls.value) == 1, cls.value)], else_=0)
             ).label("revenues"),
-            func.sum(cls.value).label("balance")
+            db.func.sum(cls.value).label("balance")
         ).filter(
             cls.account_id == account_id
         ).filter(
@@ -176,8 +178,8 @@ class Operation(db.Model):
 
         end = end if end else arrow.now().ceil('month').date()
 
-        sold = func.sum(cls.value).over(
-            order_by=[cls.operation_date, desc(cls.value), cls.label]
+        sold = db.func.sum(cls.value).over(
+            order_by=[cls.operation_date, db.desc(cls.value), cls.label]
         )
 
         previous = sold - cls.value
@@ -188,29 +190,29 @@ class Operation(db.Model):
             previous.label("previous")
         ).filter(
             cls.account_id == account_id,
-            cls.canceled == false()
+            cls.canceled == db.false()
         ).subquery()
 
         query = db.session.query(
             subquery.c.operation_date,
-            func.first_value(subquery.c.previous).over(
+            db.func.first_value(subquery.c.previous).over(
                 partition_by=subquery.c.operation_date
             ).label("open"),
-            func.max(
-                func.greatest(
+            db.func.max(
+                db.func.greatest(
                     subquery.c.previous, subquery.c.sold
                 )
             ).over(
                 partition_by=subquery.c.operation_date
             ).label('high'),
-            func.min(
-                func.least(
+            db.func.min(
+                db.func.least(
                     subquery.c.previous, subquery.c.sold
                 )
             ).over(
                 partition_by=subquery.c.operation_date
             ).label('low'),
-            func.last_value(subquery.c.sold).over(
+            db.func.last_value(subquery.c.sold).over(
                 partition_by=subquery.c.operation_date
             ).label('close')
         ).distinct()
diff --git a/accountant/api/models/scheduled_operations.py b/accountant/api/models/scheduled_operations.py
index d81a0dc..eef1c1c 100644
--- a/accountant/api/models/scheduled_operations.py
+++ b/accountant/api/models/scheduled_operations.py
@@ -16,8 +16,6 @@
 """
 from calendar import monthrange
 
-from sqlalchemy import desc, false
-
 import arrow
 
 from accountant import db
@@ -66,7 +64,7 @@ class ScheduledOperation(db.Model):
         return db.session.query(
             cls
         ).order_by(
-            desc(cls.day),
+            db.desc(cls.day),
             cls.value,
             cls.label,
         )
@@ -77,7 +75,7 @@ class ScheduledOperation(db.Model):
             Operation
         ).filter(
             Operation.scheduled_operation_id == self.id,
-            Operation.confirmed == false()
+            Operation.confirmed == db.false()
         ).delete()
 
         # 2) schedule remaining operations.
diff --git a/accountant/api/models/users.py b/accountant/api/models/users.py
index 5812163..80ac15d 100644
--- a/accountant/api/models/users.py
+++ b/accountant/api/models/users.py
@@ -23,8 +23,6 @@ from flask import current_app as app
 
 from flask.ext.login import UserMixin
 
-from sqlalchemy import true
-
 from accountant import db
 
 
@@ -33,7 +31,7 @@ class User(UserMixin, db.Model):
     email = db.Column(db.String(200), nullable=False, unique=True, index=True)
     password = db.Column(db.String(100), nullable=True)
     active = db.Column(db.Boolean, nullable=False, default=True,
-                       server_default=true())
+                       server_default=db.true())
 
     @property
     def is_active(self):