diff --git a/ihatemoney/forms.py b/ihatemoney/forms.py
index 8fd13f6d..295475e1 100644
--- a/ihatemoney/forms.py
+++ b/ihatemoney/forms.py
@@ -312,7 +312,7 @@ class MemberForm(FlaskForm):
             and Person.query.filter(
                 Person.name == field.data,
                 Person.project == form.project,
-                Person.activated == True,
+                Person.activated,
             ).all()
         ):  # NOQA
             raise ValidationError(_("This project already have this member"))
diff --git a/setup.cfg b/setup.cfg
index d632d515..4628067d 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -22,34 +22,34 @@ packages = find:
 include_package_data = True
 zip_safe = False
 install_requires =
-    blinker==1.4
-    cachetools==4.1.0
-    debts==0.5
-    email_validator==1.0.5
-    Flask-Babel==1.0.0
-    Flask-Cors==3.0.8
-    Flask-Mail==0.9.1
-    Flask-Migrate==2.5.3
-    Flask-RESTful==0.3.8
-    Flask-Script==2.0.6
-    Flask-SQLAlchemy==2.4.1
-    Flask-WTF==0.14.3
-	WTForms==2.2.1
-    Flask==1.1.2
-    itsdangerous==1.1.0
-    Jinja2==2.11.2
-    requests==2.22.0
-    SQLAlchemy-Continuum==1.3.9
+    blinker~=1.4
+    cachetools~=4.1
+    debts~=0.5
+    email_validator~=1.0
+    Flask-Babel~=1.0
+    Flask-Cors~=3.0
+    Flask-Mail~=0.9
+    Flask-Migrate>=2.5.3  # Not following semantic versioning (e.g. https://github.com/miguelgrinberg/flask-migrate/commit/1af28ba273de6c88544623b8dc02dd539340294b)
+    Flask-RESTful~=0.3
+    Flask-Script~=2.0
+    Flask-SQLAlchemy~=2.4
+    Flask-WTF~=0.14,>=0.14.3  # See b76da172652da94c1f9c4b2fdd965375da8a2c3f
+	WTForms~=2.2.1,<2.3  # See #567
+    Flask~=1.1
+    itsdangerous~=1.1
+    Jinja2~=2.11
+    requests~=2.22
+    SQLAlchemy-Continuum~=1.3
 
 [options.extras_require]
 dev =
-    black==19.10b0 ; python_version >= '3.6'
-    flake8==3.7.9
-    Flask-Testing==0.8.0
-    isort==4.3.21
-    pytest==5.4.1
-    tox==3.14.6
-    zest.releaser==6.20.1
+    black>=19.10b0 ; python_version >= '3.6'
+    flake8>=3.7.9
+    Flask-Testing>=0.8.0
+    isort>=4.3.21
+    pytest>=5.4.1
+    tox>=3.14.6
+    zest.releaser>=6.20.1
 
 [options.entry_points]
 console_scripts =