diff --git a/scripts/optimize.py b/scripts/optimize.py
index b44a66f9..09c1b39b 100644
--- a/scripts/optimize.py
+++ b/scripts/optimize.py
@@ -230,6 +230,7 @@ def get_additional_scalars():
         # Reduce number of timestep for debugging
         if config.settings.optimize.debug:
             es.timeindex = es.timeindex[:3]
+            es.timeincrement = es.timeincrement[:3]
 
             logger.info("Using DEBUG mode: Running model with first 3 timesteps only.")