diff --git a/locust/env.py b/locust/env.py
index b5e9f68ede..a51f9e326c 100644
--- a/locust/env.py
+++ b/locust/env.py
@@ -98,6 +98,11 @@ def __init__(
                     ", ".join(map(methodcaller("fullname"), self.user_classes))
                 )
             )
+        if self.shape_class is not None and not isinstance(self.shape_class, LoadTestShape):
+            raise ValueError(
+                "shape_class should be instance of LoadTestShape or subclass LoadTestShape, but got: %s"
+                % self.shape_class
+            )
 
     def _create_runner(
         self,
diff --git a/locust/test/test_env.py b/locust/test/test_env.py
index 09ba4e97a3..2db8d60171 100644
--- a/locust/test/test_env.py
+++ b/locust/test/test_env.py
@@ -1,7 +1,7 @@
 from locust import (
     constant,
 )
-from locust.env import Environment
+from locust.env import Environment, LoadTestShape
 from locust.user import (
     User,
     task,
@@ -190,3 +190,12 @@ def my_task(self):
             e.exception.args[0],
             "There are no users with weight > 0.",
         )
+
+    def test_shape_class_attribute(self):
+        class SubLoadTestShape(LoadTestShape):
+            """Inherited from locust.env.LoadTestShape"""
+
+        with self.assertRaisesRegex(
+            ValueError, r"instance of LoadTestShape or subclass LoadTestShape", msg="exception message is mismatching"
+        ):
+            Environment(user_classes=[MyUserWithSameName1], shape_class=SubLoadTestShape)