diff --git a/openquake/hme/bin/hamlet.py b/openquake/hme/bin/hamlet.py
index 97a767e..ee51663 100755
--- a/openquake/hme/bin/hamlet.py
+++ b/openquake/hme/bin/hamlet.py
@@ -68,6 +68,9 @@ def main(arg=None):
 
         if args.pdb:
             debugger.post_mortem()
+        else:
+            # Exit with non-zero error code so that tests fail
+            sys.exit(1)
 
 
 if __name__ == "__main__":