diff --git a/tests/scripts/run_demos.py b/tests/scripts/run_demos.py
index fcf13cd..6d86a9b 100755
--- a/tests/scripts/run_demos.py
+++ b/tests/scripts/run_demos.py
@@ -43,6 +43,8 @@
     Return True if all demos passed and False if a demo fails.
     """
     all_demos = glob.glob('programs/*/*_demo.sh')
+    if not all_demos:
+        raise Exception('No demos found. run_demos needs to operate from the Mbed TLS toplevel directory.')
     return run_demos(all_demos, quiet=quiet)
 
 def main():