diff --git a/scripts/test/ISISPowderRunDetailsTest.py b/scripts/test/ISISPowderRunDetailsTest.py
index 67cc059abf94ca2da0f561be88abb543b27b7052..cfde0b28f840b4ec17a9033b048e85ff6b9e545c 100644
--- a/scripts/test/ISISPowderRunDetailsTest.py
+++ b/scripts/test/ISISPowderRunDetailsTest.py
@@ -121,7 +121,7 @@ class MockInstSettings(object):
 
     @staticmethod
     def gen_random_string():
-        return ''.join(random.choice(string.lower(s)) for s in range(10))
+        return ''.join(random.choice(string.ascii_lowercase) for _ in range(10))
 
 if __name__ == "__main__":
     unittest.main()