diff --git a/src/acom_music_box/music_box.py b/src/acom_music_box/music_box.py
index fd948ba4..6cc43374 100644
--- a/src/acom_music_box/music_box.py
+++ b/src/acom_music_box/music_box.py
@@ -465,7 +465,7 @@ def solve(self, path_to_output = None):
 
 
         if (self.solver is None):
-            music_box_logger.progress("Warning: MusicBox object {} has no solver."
+            raise Exception("Error: MusicBox object {} has no solver."
                 .format(self))
         rate_constant_ordering = musica.user_defined_reaction_rates(self.solver)