diff --git a/pre_build.py b/pre_build.py
index 720afc1938..3718df8b37 100644
--- a/pre_build.py
+++ b/pre_build.py
@@ -1,8 +1,13 @@
 import os
 import subprocess
+from shutil import which
+from sys import exit
 
 
 def build() -> None:
+    if which("yarn") is None:
+        print("Locust requires the yarn binary to be available in this shell to build the web front-end.\nSee: https://docs.locust.io/en/stable/developing-locust.html#making-changes-to-locust-s-web-ui")
+        exit(1)
     if os.environ.get("SKIP_PRE_BUILD", "") == "true":
         print("Skipping front end build...")
         return