diff --git a/tests/__init__.py b/tests/__init__.py
index dc5fd7e..72c485d 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -11,6 +11,7 @@ def get_app():
     app = Flask(__name__)
 
     app.secret_key = b"%\xe0'\x01\xdeH\x8e\x85m|\xb3\xffCN\xc9g"
+    os.environ["OAUTHLIB_INSECURE_TRANSPORT"] = "true"  # !! Only in development environment.
 
     # app.config["DISCORD_CLIENT_ID"] = 490732332240863233
     app.config["DISCORD_CLIENT_SECRET"] = os.getenv("DISCORD_CLIENT_SECRET")
diff --git a/tests/test_app.py b/tests/test_app.py
index 706e23d..08c6458 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -7,6 +7,7 @@ from flask_discord import DiscordOAuth2Session, requires_authorization
 app = Flask(__name__)
 
 app.secret_key = b"%\xe0'\x01\xdeH\x8e\x85m|\xb3\xffCN\xc9g"
+os.environ["OAUTHLIB_INSECURE_TRANSPORT"] = "true"    # !! Only in development environment.
 
 app.config["DISCORD_CLIENT_ID"] = 490732332240863233
 app.config["DISCORD_CLIENT_SECRET"] = os.getenv("DISCORD_CLIENT_SECRET")