diff --git a/locust/main.py b/locust/main.py
index fa695199c1..c65703aa1e 100644
--- a/locust/main.py
+++ b/locust/main.py
@@ -324,11 +324,12 @@ def kill_workers(children):
         # list() call is needed to consume the dict_view object in Python 3
         user_classes = list(user_classes.values())
 
-    fixed_count_total = sum([user_class.fixed_count for user_class in user_classes])
-    if not shape_class and fixed_count_total > options.num_users:
-        logger.info(
-            f"Total fixed_count of User classes ({fixed_count_total}) is greater than the specified number of users ({options.num_users}), so not all will be spawned."
-        )
+    if not shape_class and options.num_users:
+        fixed_count_total = sum([user_class.fixed_count for user_class in user_classes])
+        if fixed_count_total > options.num_users:
+            logger.info(
+                f"Total fixed_count of User classes ({fixed_count_total}) is greater than the specified number of users ({options.num_users}), so not all will be spawned."
+            )
 
     if os.name != "nt" and not options.master:
         try: