diff --git a/core/planner/helper_test.go b/core/planner/helper_test.go
index c2759ea23..5f07a8698 100644
--- a/core/planner/helper_test.go
+++ b/core/planner/helper_test.go
@@ -9,9 +9,18 @@ import (
 	"github.com/evcc-io/evcc/api"
 	"github.com/evcc-io/evcc/tariff"
 	"github.com/samber/lo"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+func TestSlitPrecondition(t *testing.T) {
+	clock := clock.NewMock()
+	rr := rates([]float64{1, 2, 3, 4}, clock.Now(), tariff.SlotDuration)
+	rates, precond := splitPreconditionSlots(rr, clock.Now().Add(3*tariff.SlotDuration))
+	assert.Equal(t, rr[0:3], rates, "rates")
+	assert.Equal(t, rr[3:], precond, "precond")
+}
+
 func TestSlotHasSuccessor(t *testing.T) {
 	plan := rates([]float64{20, 60, 10, 80, 40, 90}, time.Now(), time.Hour)
 
diff --git a/core/planner/planner.go b/core/planner/planner.go
index fe34af7f7..950394c03 100644
--- a/core/planner/planner.go
+++ b/core/planner/planner.go
@@ -208,7 +208,7 @@ func splitPreconditionSlots(rates api.Rates, preCondStart time.Time) (api.Rates,
 		}
 
 		// split slot
-		if !r.Start.After(preCondStart) {
+		if r.Start.Before(preCondStart) {
 			// keep the first part of the slot
 			res = append(res, api.Rate{
 				Start: r.Start,