diff --git a/reframe/core/exceptions.py b/reframe/core/exceptions.py
index 6f63402ef3..5223bf6490 100644
--- a/reframe/core/exceptions.py
+++ b/reframe/core/exceptions.py
@@ -366,7 +366,7 @@ def what(exc_type, exc_value, tb):
     elif is_user_error(exc_type, exc_value, tb):
         frame = user_frame(exc_type, exc_value, tb)
         relpath = os.path.relpath(frame.filename)
-        source = ''.join(frame.code_context)
+        source = ''.join(frame.code_context or '<n/a>')
         reason += f': {relpath}:{frame.lineno}: {exc_value}\n{source}'
     else:
         if str(exc_value):