diff --git a/deps/buildcore/scripts/pybb.py b/deps/buildcore/scripts/pybb.py
index 1036d7e4..42860895 100755
--- a/deps/buildcore/scripts/pybb.py
+++ b/deps/buildcore/scripts/pybb.py
@@ -98,6 +98,9 @@ def debug(paths: List[str]) -> int:
         args = ['gdb', '--args']
     elif shutil.which('lldb') is not None:
         args = ['lldb', '--']
+    else:
+        sys.stderr.write('debug: could not find a supported debugger\n')
+        return 1
     args.extend(paths)
     return subprocess.run(args).returncode