diff --git a/core/site_optimizer.go b/core/site_optimizer.go
index 2c1eac0e1..ad1b92120 100644
--- a/core/site_optimizer.go
+++ b/core/site_optimizer.go
@@ -200,7 +200,9 @@ func (site *Site) optimizerUpdate(battery []measurement) error {
 
 		case api.ModeNow, api.ModeMinPV:
 			// forced min/max charging
-			bat.PDemand = prorate(continuousDemand(lp, minLen), firstSlotDuration)
+			if demand := continuousDemand(lp, minLen); demand != nil {
+				bat.PDemand = prorate(demand, firstSlotDuration)
+			}
 
 		case api.ModePV:
 			// add plan goal